--- a/accessible/atk/moz.build
+++ b/accessible/atk/moz.build
@@ -49,15 +49,15 @@ if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']
     CFLAGS += CONFIG['TK_CFLAGS']
     CXXFLAGS += CONFIG['TK_CFLAGS']
 
 if CONFIG['MOZ_ENABLE_DBUS']:
     CXXFLAGS += CONFIG['MOZ_DBUS_CFLAGS']
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
-if CONFIG['CLANG_CXX'] or CONFIG['GNU_CXX']:
+if CONFIG['CLANG_CXX'] or CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     # Used in G_DEFINE_TYPE_EXTENDED macro, probably fixed in newer glib /
     # gobject headers. See bug 1243331 comment 3.
     CXXFLAGS += [
         '-Wno-error=shadow',
         '-Wno-unused-local-typedefs',
     ]

--- a/accessible/base/moz.build
+++ b/accessible/base/moz.build
@@ -107,10 +107,10 @@ else:
     LOCAL_INCLUDES += [
         '/accessible/other',
     ]
 
 FINAL_LIBRARY = 'xul'
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/accessible/generic/moz.build
+++ b/accessible/generic/moz.build
@@ -61,10 +61,10 @@ else:
     LOCAL_INCLUDES += [
         '/accessible/other',
     ]
 
 FINAL_LIBRARY = 'xul'
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/accessible/html/moz.build
+++ b/accessible/html/moz.build
@@ -41,10 +41,10 @@ else:
     LOCAL_INCLUDES += [
         '/accessible/other',
     ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/accessible/ipc/moz.build
+++ b/accessible/ipc/moz.build
@@ -28,17 +28,17 @@ else:
         LOCAL_INCLUDES += [
             '/accessible/other',
         ]
 
 EXPORTS.mozilla.a11y += [
     'IPCTypes.h',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 if CONFIG['ACCESSIBILITY']:
     EXPORTS.mozilla.a11y += [
         'DocAccessibleChildBase.h',
         'DocAccessibleParent.h',
         'ProxyAccessibleBase.h',
         'ProxyAccessibleShared.h',

--- a/accessible/ipc/other/moz.build
+++ b/accessible/ipc/other/moz.build
@@ -35,13 +35,13 @@ if CONFIG['ACCESSIBILITY']:
         ]
     else:
         LOCAL_INCLUDES += [
             '/accessible/other',
         ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 FINAL_LIBRARY = 'xul'
 

--- a/accessible/other/moz.build
+++ b/accessible/other/moz.build
@@ -18,10 +18,10 @@ LOCAL_INCLUDES += [
     '/accessible/base',
     '/accessible/generic',
     '/accessible/html',
     '/accessible/xul',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/accessible/xpcom/moz.build
+++ b/accessible/xpcom/moz.build
@@ -57,10 +57,10 @@ GENERATED_FILES += [('xpcAccEvents.h', '
 xpc_acc = GENERATED_FILES[('xpcAccEvents.h', 'xpcAccEvents.cpp')]
 xpc_acc.script = 'AccEventGen.py:gen_files'
 xpc_acc.inputs += ['AccEvents.conf', '!/xpcom/idl-parser/xpidl/xpidllex.py', '!/xpcom/idl-parser/xpidl/xpidlyacc.py']
 
 FINAL_LIBRARY = 'xul'
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/accessible/xul/moz.build
+++ b/accessible/xul/moz.build
@@ -48,10 +48,10 @@ else:
     LOCAL_INCLUDES += [
         '/accessible/other',
     ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/browser/app/moz.build
+++ b/browser/app/moz.build
@@ -90,17 +90,17 @@ if CONFIG['MOZ_SANDBOX'] and CONFIG['OS_
 # Control the default heap size.
 # This is the heap returned by GetProcessHeap().
 # As we use the CRT heap, the default size is too large and wastes VM.
 #
 # The default heap size is 1MB on Win32.
 # The heap will grow if need be.
 #
 # Set it to 256k.  See bug 127069.
-if CONFIG['OS_ARCH'] == 'WINNT' and not CONFIG['GNU_CC']:
+if CONFIG['OS_ARCH'] == 'WINNT' and CONFIG['CC_TYPE'] not in ('clang', 'gcc'):
     LDFLAGS += ['/HEAP:0x40000']
 
 DisableStlWrapping()
 
 if CONFIG['MOZ_LINKER']:
     OS_LIBS += CONFIG['MOZ_ZLIB_LIBS']
 
 if CONFIG['HAVE_CLOCK_MONOTONIC']:

--- a/build/gecko_templates.mozbuild
+++ b/build/gecko_templates.mozbuild
@@ -36,17 +36,17 @@ def GeckoBinary(linkage='dependent', moz
     elif linkage != None:
         error('`linkage` must be "dependent", "standalone" or None')
 
     if mozglue:
         LDFLAGS += CONFIG['MOZ_GLUE_WRAP_LDFLAGS']
         if mozglue == 'program':
             USE_LIBS += ['mozglue']
             DEFINES['MOZ_HAS_MOZGLUE'] = True
-            if CONFIG['MOZ_GLUE_IN_PROGRAM'] and CONFIG['GNU_CC']:
+            if CONFIG['MOZ_GLUE_IN_PROGRAM'] and CONFIG['CC_TYPE'] in ('clang', 'gcc'):
                 LDFLAGS += ['-rdynamic']
         elif mozglue == 'library':
             LIBRARY_DEFINES['MOZ_HAS_MOZGLUE'] = True
             if not CONFIG['MOZ_GLUE_IN_PROGRAM']:
                 USE_LIBS += ['mozglue']
         else:
             error('`mozglue` must be "program" or "library"')
 

--- a/config/external/icu/common/moz.build
+++ b/config/external/icu/common/moz.build
@@ -6,17 +6,17 @@
 
 Library('icuuc')
 FINAL_LIBRARY = 'icu'
 
 DEFINES['U_COMMON_IMPLEMENTATION'] = True
 
 LOCAL_INCLUDES += ['/intl/icu/source/i18n']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += [
         '-Wno-deprecated-declarations',
         '-Wno-type-limits',
         '-Wno-unused-but-set-variable',
         '-Wno-unused-function',
         '-Wno-sign-compare',
         '-Wno-maybe-uninitialized',
     ]

--- a/config/external/icu/defs.mozbuild
+++ b/config/external/icu/defs.mozbuild
@@ -22,17 +22,17 @@ DEFINES.update(
 
 if not CONFIG['HAVE_LANGINFO_CODESET']:
     DEFINES['U_HAVE_NL_LANGINFO_CODESET'] = 0
 
 if CONFIG['MOZ_DEBUG']:
     DEFINES['U_DEBUG'] = 1
 
 # ICU requires RTTI
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-frtti']
 elif CONFIG['OS_TARGET'] == 'WINNT':
     CXXFLAGS += ['-GR']
 
 DisableStlWrapping()
 AllowCompilerWarnings()
 
 # We allow compiler warnings, but we can at least cut down on spammy

--- a/config/moz.build
+++ b/config/moz.build
@@ -30,28 +30,28 @@ if CONFIG['HOST_OS_ARCH'] != 'WINNT':
 
 if CONFIG['MOZ_SYSTEM_ICU']:
     DEFINES['MOZ_SYSTEM_ICU'] = True
 
 PYTHON_UNITTEST_MANIFESTS += [
     'tests/python.ini',
 ]
 
-if CONFIG['GNU_CC'] and CONFIG['MOZ_OPTIMIZE']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') and CONFIG['MOZ_OPTIMIZE']:
     CFLAGS += ['-O3']
 
 HOST_DEFINES = {
     'UNICODE': True,
     '_UNICODE': True,
 }
 
 include('stl-headers.mozbuild')
 if CONFIG['WRAP_STL_INCLUDES']:
     stl_compiler = None
-    if CONFIG['GNU_CXX']:
+    if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         stl_compiler = 'gcc'
     elif CONFIG['_MSC_VER']:
         stl_compiler = 'msvc'
 
     if stl_compiler:
         template_file = SRCDIR + '/%s-stl-wrapper.template.h' % stl_compiler
         output_dir = '../dist/stl_wrappers'
         # We have to use a sentinel file as the first file because the

--- a/db/sqlite3/src/moz.build
+++ b/db/sqlite3/src/moz.build
@@ -89,13 +89,13 @@ DEFINES['SQLITE_OMIT_DECLTYPE'] = True
 if CONFIG['OS_TARGET'] == 'Android':
     # On Android there's no tmp partition, so always use a MEMORY temp store.
     DEFINES['SQLITE_TEMP_STORE'] = 3
 elif CONFIG['HAVE_64BIT_BUILD']:
     # On 64bit platforms default to a MEMORY temp store for performance.
     DEFINES['SQLITE_TEMP_STORE'] = 2
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CFLAGS += [
         '-Wno-sign-compare',
         '-Wno-type-limits',
     ]

--- a/devtools/shared/heapsnapshot/moz.build
+++ b/devtools/shared/heapsnapshot/moz.build
@@ -53,10 +53,10 @@ DevToolsModules(
     'CensusUtils.js',
     'DominatorTreeNode.js',
     'HeapAnalysesClient.js',
     'HeapAnalysesWorker.js',
     'HeapSnapshotFileUtils.js',
     'shortest-paths.js',
 )
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/devtools/shared/heapsnapshot/tests/gtest/moz.build
+++ b/devtools/shared/heapsnapshot/tests/gtest/moz.build
@@ -18,17 +18,17 @@ UNIFIED_SOURCES = [
     'DeserializedStackFrameUbiStackFrames.cpp',
     'DoesCrossCompartmentBoundaries.cpp',
     'DoesntCrossCompartmentBoundaries.cpp',
     'SerializesEdgeNames.cpp',
     'SerializesEverythingInHeapGraphOnce.cpp',
     'SerializesTypeNames.cpp',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 # THE MOCK_METHOD2 macro from gtest triggers this clang warning and it's hard
 # to work around, so we just ignore it.
 if CONFIG['CLANG_CXX']:
   CXXFLAGS += ['-Wno-inconsistent-missing-override']
   # Workaround bug 1142396. Suppress the warning from gmock library for clang.
   CXXFLAGS += ['-Wno-null-dereference']

--- a/docshell/base/moz.build
+++ b/docshell/base/moz.build
@@ -117,10 +117,10 @@ LOCAL_INCLUDES += [
     '/netwerk/protocol/viewsource',
     '/toolkit/components/browser',
     '/tools/profiler',
 ]
 
 if CONFIG['MOZ_TOOLKIT_SEARCH']:
     DEFINES['MOZ_TOOLKIT_SEARCH'] = True
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/docshell/shistory/moz.build
+++ b/docshell/shistory/moz.build
@@ -31,10 +31,10 @@ UNIFIED_SOURCES += [
 ]
 
 LOCAL_INCLUDES += [
     '/docshell/base',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/base/moz.build
+++ b/dom/base/moz.build
@@ -480,10 +480,10 @@ GENERATED_FILES += [
 countermap = GENERATED_FILES['PropertyUseCounterMap.inc']
 countermap.script = 'gen-usecounters.py:property_map'
 countermap.inputs = ['UseCounters.conf']
 
 counterlist = GENERATED_FILES['UseCounterList.h']
 counterlist.script = 'gen-usecounters.py:use_counter_list'
 counterlist.inputs = ['UseCounters.conf']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/bindings/moz.build
+++ b/dom/bindings/moz.build
@@ -155,17 +155,17 @@ if CONFIG['MOZ_BUILD_APP'] in ['browser'
     # This is needed for Window.webidl
     DEFINES['HAVE_SIDEBAR'] = True
 
 
 PYTHON_UNITTEST_MANIFESTS += [
     'mozwebidlcodegen/test/python.ini',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
     # Suppress warnings in third-party code.
     CXXFLAGS += [
         '-Wno-maybe-uninitialized',
     ]
 
 if CONFIG['COMPILE_ENVIRONMENT']:
     GENERATED_FILES += ['CSS2Properties.webidl']

--- a/dom/bindings/test/moz.build
+++ b/dom/bindings/test/moz.build
@@ -49,10 +49,10 @@ LOCAL_INCLUDES += [
 
 LOCAL_INCLUDES += [
     '!..',
     '/dom/bindings',
     '/js/xpconnect/src',
     '/js/xpconnect/wrappers',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/cache/moz.build
+++ b/dom/cache/moz.build
@@ -95,10 +95,10 @@ MOCHITEST_MANIFESTS += [
 BROWSER_CHROME_MANIFESTS += [
     'test/mochitest/browser.ini',
 ]
 
 XPCSHELL_TESTS_MANIFESTS += [
     'test/xpcshell/xpcshell.ini',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/canvas/moz.build
+++ b/dom/canvas/moz.build
@@ -184,17 +184,17 @@ UNIFIED_SOURCES += [
     'WebGLVertexAttribData.cpp',
 ]
 
 SOURCES += [
     'MurmurHash3.cpp',
 ]
 
 # Suppress warnings from third-party code.
-if CONFIG['CLANG_CXX'] or CONFIG['GNU_CXX']:
+if CONFIG['CLANG_CXX'] or CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     SOURCES['MurmurHash3.cpp'].flags += ['-Wno-implicit-fallthrough']
 
 LOCAL_INCLUDES += [
     '/js/xpconnect/wrappers',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
@@ -215,10 +215,10 @@ LOCAL_INCLUDES += [
     '/media/libyuv/libyuv/include',
 ]
 
 CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 CXXFLAGS += CONFIG['TK_CFLAGS']
 
 LOCAL_INCLUDES += CONFIG['SKIA_INCLUDES']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/events/moz.build
+++ b/dom/events/moz.build
@@ -152,10 +152,10 @@ LOCAL_INCLUDES += [
     '/dom/xml',
     '/dom/xul',
     '/js/xpconnect/wrappers',
     '/layout/generic',
     '/layout/xul',
     '/layout/xul/tree/',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/file/ipc/moz.build
+++ b/dom/file/ipc/moz.build
@@ -48,13 +48,13 @@ LOCAL_INCLUDES += [
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
 CXXFLAGS += CONFIG['TK_CFLAGS']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 BROWSER_CHROME_MANIFESTS += ['tests/browser.ini']
 MOCHITEST_MANIFESTS += ['tests/mochitest.ini']

--- a/dom/html/input/moz.build
+++ b/dom/html/input/moz.build
@@ -30,11 +30,11 @@ include('/ipc/chromium/chromium-config.m
 LOCAL_INCLUDES += [
     '/dom/base',
     '/dom/html',
     '/layout/forms',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 

--- a/dom/html/moz.build
+++ b/dom/html/moz.build
@@ -246,10 +246,10 @@ LOCAL_INCLUDES += [
     '/netwerk/base',
 ]
 
 FINAL_LIBRARY = 'xul'
 
 if CONFIG['MOZ_ANDROID_HLS_SUPPORT'] and CONFIG['MOZ_BUILD_MOBILE_ANDROID_WITH_GRADLE']:
     DEFINES['MOZ_ANDROID_HLS_SUPPORT'] = True
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/indexedDB/moz.build
+++ b/dom/indexedDB/moz.build
@@ -90,17 +90,17 @@ IPDL_SOURCES += [
     'PBackgroundIndexedDBUtils.ipdl',
     'PIndexedDBPermissionRequest.ipdl',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     # Suppress gcc warning about a comparison being always false due to the
     # range of the data type
     SOURCES['Key.cpp'].flags += ['-Wno-error=type-limits']
     CXXFLAGS += ['-Wno-error=shadow']
 
 LOCAL_INCLUDES += [
     '/db/sqlite3/src',
     '/dom/base',

--- a/dom/ipc/moz.build
+++ b/dom/ipc/moz.build
@@ -168,10 +168,10 @@ if CONFIG['MOZ_TOOLKIT_SEARCH']:
 JAR_MANIFESTS += ['jar.mn']
 
 BROWSER_CHROME_MANIFESTS += ['tests/browser.ini']
 MOCHITEST_CHROME_MANIFESTS += ['tests/chrome.ini']
 MOCHITEST_MANIFESTS += ['tests/mochitest.ini']
 
 CXXFLAGS += CONFIG['TK_CFLAGS']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/bridge/moz.build
+++ b/dom/media/bridge/moz.build
@@ -23,10 +23,10 @@ LOCAL_INCLUDES += [
     '/media/webrtc/signaling/src/media-conduit',
     '/media/webrtc/signaling/src/mediapipeline',
     '/media/webrtc/signaling/src/peerconnection',
     '/media/webrtc/trunk/',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/doctor/gtest/moz.build
+++ b/dom/media/doctor/gtest/moz.build
@@ -12,10 +12,10 @@ UNIFIED_SOURCES += [
 include('/ipc/chromium/chromium-config.mozbuild')
 
 LOCAL_INCLUDES += [
     '/dom/media/doctor',
 ]
 
 FINAL_LIBRARY = 'xul-gtest'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/encoder/moz.build
+++ b/dom/media/encoder/moz.build
@@ -34,10 +34,10 @@ FINAL_LIBRARY = 'xul'
 # These includes are from Android JB, for use of MediaCodec.
 LOCAL_INCLUDES += ['/ipc/chromium/src']
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 # Suppress some GCC warnings being treated as errors:
 #  - about attributes on forward declarations for types that are already
 #    defined, which complains about an important MOZ_EXPORT for android::AString
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
   CXXFLAGS += ['-Wno-error=attributes']

--- a/dom/media/flac/moz.build
+++ b/dom/media/flac/moz.build
@@ -15,10 +15,10 @@ UNIFIED_SOURCES += [
     'FlacDemuxer.cpp',
     'FlacFrameParser.cpp',
 ]
 
 CXXFLAGS += CONFIG['MOZ_LIBVPX_CFLAGS']
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/gmp/moz.build
+++ b/dom/media/gmp/moz.build
@@ -136,10 +136,10 @@ FINAL_LIBRARY = 'xul'
 # media/mtransport so we work with --disable-webrtc
 LOCAL_INCLUDES += [
     '/media/mtransport',
     '/xpcom/base',
     '/xpcom/build',
     '/xpcom/threads',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/gtest/moz.build
+++ b/dom/media/gtest/moz.build
@@ -70,10 +70,10 @@ LOCAL_INCLUDES += [
     '/dom/media/platforms',
     '/dom/media/platforms/agnostic',
     '/security/certverifier',
     '/security/pkix/include',
 ]
 
 FINAL_LIBRARY = 'xul-gtest'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/hls/moz.build
+++ b/dom/media/hls/moz.build
@@ -15,10 +15,10 @@ UNIFIED_SOURCES += [
     'HLSDemuxer.cpp',
     'HLSUtils.cpp',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/mediasink/moz.build
+++ b/dom/media/mediasink/moz.build
@@ -9,10 +9,10 @@ UNIFIED_SOURCES += [
     'AudioSinkWrapper.cpp',
     'DecodedStream.cpp',
     'OutputStreamManager.cpp',
     'VideoSink.cpp',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/mediasource/moz.build
+++ b/dom/media/mediasource/moz.build
@@ -37,10 +37,10 @@ UNIFIED_SOURCES += [
 TEST_DIRS += [
     'gtest',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/moz.build
+++ b/dom/media/moz.build
@@ -291,17 +291,17 @@ if CONFIG['OS_TARGET'] == 'WINNT':
 # DecoderTraits.cpp needs to be built separately because of Mac OS X headers.
 SOURCES += [
     'CubebUtils.cpp',
     'DecoderTraits.cpp',
 ]
 
 # Some codec-related code uses multi-character constants, which GCC and clang
 # warn about. Suppress turning this warning into an error.
-if CONFIG['GNU_CC'] or CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']:
   SOURCES['DecoderTraits.cpp'].flags += ['-Wno-error=multichar']
 
 EXTRA_COMPONENTS += [
     'PeerConnection.js',
     'PeerConnection.manifest',
 ]
 
 EXTRA_JS_MODULES.media += [
@@ -329,15 +329,15 @@ DEFINES['MOZILLA_INTERNAL_API'] = True
 if CONFIG['MOZ_ANDROID_HLS_SUPPORT'] and CONFIG['MOZ_BUILD_MOBILE_ANDROID_WITH_GRADLE']:
     DEFINES['MOZ_ANDROID_HLS_SUPPORT'] = True
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 # Suppress some GCC warnings being treated as errors:
 #  - about attributes on forward declarations for types that are already
 #    defined, which complains about an important MOZ_EXPORT for android::AString
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += [
         '-Wno-error=attributes',
         '-Wno-error=shadow',
     ]
 
 FINAL_LIBRARY = 'xul'

--- a/dom/media/mp4/moz.build
+++ b/dom/media/mp4/moz.build
@@ -50,17 +50,17 @@ if CONFIG['_MSC_VER']:
         '-wd4018', # '<' : signed/unsigned mismatch
         '-wd4275', # non dll-interface class used as base for dll-interface class
         '-wd4305', # '=' : truncation from 'double' to 'float'
         '-wd4309', # '=' : truncation of constant value
         '-wd4355', # 'this' : used in base member initializer list
         '-wd4804', # '>' : unsafe use of type 'bool' in operation
         '-wd4099', # mismatched class/struct tags
     ]
-elif CONFIG['GNU_CXX']:
+elif CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CFLAGS += [
         '-Wno-comment',
         '-Wno-sign-compare',
         '-Wno-unused-function',
     ]
     CXXFLAGS += [
         '-Werror=format',
         '-Wno-multichar',

--- a/dom/media/platforms/agnostic/bytestreams/moz.build
+++ b/dom/media/platforms/agnostic/bytestreams/moz.build
@@ -35,17 +35,17 @@ if CONFIG['_MSC_VER']:
         '-wd4018', # '<' : signed/unsigned mismatch
         '-wd4275', # non dll-interface class used as base for dll-interface class
         '-wd4305', # '=' : truncation from 'double' to 'float'
         '-wd4309', # '=' : truncation of constant value
         '-wd4355', # 'this' : used in base member initializer list
         '-wd4804', # '>' : unsafe use of type 'bool' in operation
         '-wd4099', # mismatched class/struct tags
     ]
-elif CONFIG['GNU_CXX']:
+elif CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CFLAGS += [
         '-Wno-comment',
         '-Wno-sign-compare',
         '-Wno-unused-function',
     ]
     CXXFLAGS += [
         '-Werror=format',
         '-Wno-multichar',

--- a/dom/media/platforms/ffmpeg/ffmpeg57/moz.build
+++ b/dom/media/platforms/ffmpeg/ffmpeg57/moz.build
@@ -10,16 +10,16 @@ UNIFIED_SOURCES += [
     '../FFmpegDecoderModule.cpp',
     '../FFmpegVideoDecoder.cpp',
 ]
 LOCAL_INCLUDES += [
     '..',
     'include',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
   CXXFLAGS += [ '-Wno-deprecated-declarations' ]
 if CONFIG['CLANG_CXX']:
   CXXFLAGS += [
     '-Wno-unknown-attributes',
   ]
 
 FINAL_LIBRARY = 'xul'

--- a/dom/media/platforms/ffmpeg/ffvpx/moz.build
+++ b/dom/media/platforms/ffmpeg/ffvpx/moz.build
@@ -23,17 +23,17 @@ LOCAL_INCLUDES += [
     '../ffmpeg57/include',
 ]
 
 if CONFIG['OS_ARCH'] == 'WINNT':
     LOCAL_INCLUDES += [
         '../ffmpeg57/include',
     ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
   CXXFLAGS += [ '-Wno-deprecated-declarations' ]
 if CONFIG['CLANG_CXX']:
   CXXFLAGS += [
     '-Wno-unknown-attributes',
   ]
 if CONFIG['_MSC_VER']:
   CXXFLAGS += [
     '-wd4996', # deprecated declaration

--- a/dom/media/platforms/ffmpeg/libav55/moz.build
+++ b/dom/media/platforms/ffmpeg/libav55/moz.build
@@ -10,16 +10,16 @@ UNIFIED_SOURCES += [
     '../FFmpegDecoderModule.cpp',
     '../FFmpegVideoDecoder.cpp',
 ]
 LOCAL_INCLUDES += [
     '..',
     'include',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
   CXXFLAGS += [ '-Wno-deprecated-declarations' ]
 if CONFIG['CLANG_CXX']:
   CXXFLAGS += [
     '-Wno-unknown-attributes',
   ]
 
 FINAL_LIBRARY = 'xul'

--- a/dom/media/platforms/moz.build
+++ b/dom/media/platforms/moz.build
@@ -94,10 +94,10 @@ if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'andr
     ]
     UNIFIED_SOURCES += [
         'android/AndroidDecoderModule.cpp',
         'android/RemoteDataDecoder.cpp',
     ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/platforms/omx/moz.build
+++ b/dom/media/platforms/omx/moz.build
@@ -18,17 +18,17 @@ UNIFIED_SOURCES += [
 LOCAL_INCLUDES += [
     '/media/openmax_il/il112',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 if CONFIG['_MSC_VER']:
     # Avoid warnings from third-party code that we can not modify.
     if CONFIG['CLANG_CL']:
         CXXFLAGS += ['-Wno-invalid-source-encoding']
     else:
         CXXFLAGS += ['-validate-charset-']

--- a/dom/media/systemservices/moz.build
+++ b/dom/media/systemservices/moz.build
@@ -83,10 +83,10 @@ IPDL_SOURCES += [
 LOCAL_INCLUDES += [
     '/dom/base',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/wave/moz.build
+++ b/dom/media/wave/moz.build
@@ -11,10 +11,10 @@ EXPORTS += [
 
 UNIFIED_SOURCES += [
     'WaveDecoder.cpp',
     'WaveDemuxer.cpp',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/webaudio/blink/moz.build
+++ b/dom/media/webaudio/blink/moz.build
@@ -30,10 +30,10 @@ if CONFIG['INTEL_ARCHITECTURE']:
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 LOCAL_INCLUDES += [
     '/dom/media/webaudio',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-shadow']

--- a/dom/media/webaudio/moz.build
+++ b/dom/media/webaudio/moz.build
@@ -128,10 +128,10 @@ if CONFIG['INTEL_ARCHITECTURE']:
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 LOCAL_INCLUDES += [
     '..'
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/webm/moz.build
+++ b/dom/media/webm/moz.build
@@ -22,10 +22,10 @@ if CONFIG['MOZ_WEBM_ENCODER']:
     UNIFIED_SOURCES += ['EbmlComposer.cpp',
                         'WebMWriter.cpp',
     ]
 
 CXXFLAGS += CONFIG['MOZ_LIBVPX_CFLAGS']
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/webrtc/moz.build
+++ b/dom/media/webrtc/moz.build
@@ -65,17 +65,17 @@ EXPORTS.mozilla.dom += [
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 # Suppress some GCC/clang warnings being treated as errors:
 #  - about attributes on forward declarations for types that are already
 #    defined, which complains about important MOZ_EXPORT attributes for
 #    android API types
-if CONFIG['GNU_CC'] or CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']:
     CXXFLAGS += [
         '-Wno-error=attributes',
         '-Wno-error=shadow',
     ]
 
 FINAL_LIBRARY = 'xul'
 
 if CONFIG['_MSC_VER']:

--- a/dom/media/webspeech/recognition/moz.build
+++ b/dom/media/webspeech/recognition/moz.build
@@ -48,10 +48,10 @@ LOCAL_INCLUDES += [
     '/dom/base',
     '/media/sphinxbase',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/media/webspeech/synth/moz.build
+++ b/dom/media/webspeech/synth/moz.build
@@ -58,10 +58,10 @@ IPDL_SOURCES += [
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 LOCAL_INCLUDES += [
     'ipc',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/network/moz.build
+++ b/dom/network/moz.build
@@ -54,10 +54,10 @@ IPDL_SOURCES += [
 LOCAL_INCLUDES += [
     '../workers',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/notification/moz.build
+++ b/dom/notification/moz.build
@@ -35,10 +35,10 @@ LOCAL_INCLUDES += [
     '/dom/base',
     '/dom/ipc',
     '/dom/workers',
 ]
 
 BROWSER_CHROME_MANIFESTS += ['test/browser/browser.ini']
 XPCSHELL_TESTS_MANIFESTS += ['test/unit/xpcshell.ini']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/plugins/base/moz.build
+++ b/dom/plugins/base/moz.build
@@ -83,10 +83,10 @@ if CONFIG['OS_ARCH'] == 'WINNT':
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
 CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 CXXFLAGS += CONFIG['TK_CFLAGS']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/plugins/ipc/hangui/moz.build
+++ b/dom/plugins/ipc/hangui/moz.build
@@ -12,16 +12,16 @@ UNIFIED_SOURCES += [
 ]
 include('/ipc/chromium/chromium-config.mozbuild')
 
 DEFINES['NS_NO_XPCOM'] = True
 DEFINES['_HAS_EXCEPTIONS'] = 0
 
 DisableStlWrapping()
 
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     WIN32_EXE_LDFLAGS += ['-municode']
 
 RCINCLUDE = 'HangUIDlg.rc'
 
 OS_LIBS += [
     'comctl32',
 ]

--- a/dom/plugins/ipc/moz.build
+++ b/dom/plugins/ipc/moz.build
@@ -131,17 +131,17 @@ DEFINES['FORCE_PR_LOG'] = True
 if CONFIG['MOZ_WIDGET_TOOLKIT'] != 'gtk3':
     CXXFLAGS += CONFIG['TK_CFLAGS']
 else:
     # Force build against gtk+2 for struct offsets and such.
     CXXFLAGS += CONFIG['MOZ_GTK2_CFLAGS']
 
 CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 if CONFIG['_MSC_VER']:
     # This is intended as a temporary hack to support building with VS2015.
     # conversion from 'X' to 'Y' requires a narrowing conversion
     CXXFLAGS += ['-wd4838']
 
     # 'type cast': conversion from 'unsigned int' to 'HIMC' of greater size

--- a/dom/plugins/test/testplugin/testplugin.mozbuild
+++ b/dom/plugins/test/testplugin/testplugin.mozbuild
@@ -61,10 +61,10 @@ if CONFIG['_MSC_VER']:
     CXXFLAGS += ['-wd4838']
 
 if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'cocoa':
     FINAL_TARGET = 'dist/plugins/%s.plugin/Contents/MacOS' % cocoa_name
     OBJDIR_FILES.dist.plugins['%s.plugin' % cocoa_name].Contents += ['%s/Info.plist' % relative_path]
 else:
     FINAL_TARGET = 'dist/plugins'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/promise/moz.build
+++ b/dom/promise/moz.build
@@ -30,10 +30,10 @@ include('/ipc/chromium/chromium-config.m
 FINAL_LIBRARY = 'xul'
 
 MOCHITEST_MANIFESTS += ['tests/mochitest.ini']
 
 MOCHITEST_CHROME_MANIFESTS += ['tests/chrome.ini']
 
 XPCSHELL_TESTS_MANIFESTS += ['tests/unit/xpcshell.ini']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/quota/moz.build
+++ b/dom/quota/moz.build
@@ -61,10 +61,10 @@ IPDL_SOURCES += [
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 LOCAL_INCLUDES += [
     '../workers',
     '/caps',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/svg/moz.build
+++ b/dom/svg/moz.build
@@ -267,10 +267,10 @@ LOCAL_INCLUDES += [
     '/dom/xml',
     '/layout/base',
     '/layout/generic',
     '/layout/style',
     '/layout/svg',
     '/layout/xul',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/webbrowserpersist/moz.build
+++ b/dom/webbrowserpersist/moz.build
@@ -44,10 +44,10 @@ EXPORTS.mozilla += [
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 LOCAL_INCLUDES += [
     '/dom/base',
     '/dom/html',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/workers/moz.build
+++ b/dom/workers/moz.build
@@ -135,10 +135,10 @@ BROWSER_CHROME_MANIFESTS += [
 ]
 
 XPCSHELL_TESTS_MANIFESTS += ['test/xpcshell/xpcshell.ini']
 
 BROWSER_CHROME_MANIFESTS += ['test/browser.ini']
 
 TEST_DIRS += ['test/gtest']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/xbl/moz.build
+++ b/dom/xbl/moz.build
@@ -48,10 +48,10 @@ LOCAL_INCLUDES += [
     '/layout/style',
 ]
 
 FINAL_LIBRARY = 'xul'
 
 MOCHITEST_MANIFESTS += ['test/mochitest.ini']
 MOCHITEST_CHROME_MANIFESTS += ['test/chrome.ini']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/xslt/base/moz.build
+++ b/dom/xslt/base/moz.build
@@ -17,10 +17,10 @@ LOCAL_INCLUDES += [
     '..',
     '../xml',
     '../xpath',
     '../xslt',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/xslt/xpath/moz.build
+++ b/dom/xslt/xpath/moz.build
@@ -53,10 +53,10 @@ UNIFIED_SOURCES += [
 LOCAL_INCLUDES += [
     '../base',
     '../xml',
     '../xslt',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/xslt/xslt/moz.build
+++ b/dom/xslt/xslt/moz.build
@@ -53,10 +53,10 @@ LOCAL_INCLUDES += [
     '../base',
     '../xml',
     '../xpath',
     '/dom/base',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/xul/moz.build
+++ b/dom/xul/moz.build
@@ -54,10 +54,10 @@ LOCAL_INCLUDES += [
     '/layout/base',
     '/layout/generic',
     '/layout/style',
     '/layout/xul',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/dom/xul/templates/moz.build
+++ b/dom/xul/templates/moz.build
@@ -55,10 +55,10 @@ UNIFIED_SOURCES += [
 LOCAL_INCLUDES += [
     '/dom/base',
     '/dom/xul',
     '/layout/xul/tree/',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/editor/composer/moz.build
+++ b/editor/composer/moz.build
@@ -49,10 +49,10 @@ RESOURCE_FILES += [
     'res/table-remove-column-active.gif',
     'res/table-remove-column-hover.gif',
     'res/table-remove-column.gif',
     'res/table-remove-row-active.gif',
     'res/table-remove-row-hover.gif',
     'res/table-remove-row.gif',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/editor/libeditor/moz.build
+++ b/editor/libeditor/moz.build
@@ -92,10 +92,10 @@ EXTRA_COMPONENTS += [
     'EditorUtils.js',
     'EditorUtils.manifest',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/extensions/cookie/moz.build
+++ b/extensions/cookie/moz.build
@@ -17,13 +17,13 @@ UNIFIED_SOURCES += [
 LOCAL_INCLUDES += [
     '/caps',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 with Files('**'):
     BUG_COMPONENT = ('Core', 'Networking: Cookies')

--- a/extensions/spellcheck/src/moz.build
+++ b/extensions/spellcheck/src/moz.build
@@ -25,10 +25,10 @@ else:
 LOCAL_INCLUDES += [
     '../hunspell/glue',
     '/dom/base',
 ]
 EXPORTS.mozilla += [
      'mozSpellChecker.h',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/gfx/2d/moz.build
+++ b/gfx/2d/moz.build
@@ -194,17 +194,17 @@ UNIFIED_SOURCES += [
 SOURCES += [
     'Factory.cpp', # Need to suppress warnings in Skia header files.
     'InlineTranslator.cpp',
 ]
 
 if CONFIG['CLANG_CXX']:
     SOURCES['Factory.cpp'].flags += ['-Wno-implicit-fallthrough']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'cocoa':
     EXPORTS.mozilla.gfx += [
         'QuartzSupport.h',
     ]
     SOURCES += [
         'MacIOSurface.cpp',

--- a/gfx/angle/moz.build
+++ b/gfx/angle/moz.build
@@ -135,17 +135,17 @@ if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'coco
         'src/common/system_utils_mac.cpp',
     ]
 if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'windows':
     UNIFIED_SOURCES += [
         'src/common/system_utils_win.cpp',
     ]
 
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += [
         '-Wno-attributes',
         '-Wno-shadow',
         '-Wno-sign-compare',
         '-Wno-unknown-pragmas',
         '-Wno-unreachable-code',
     ]
     if CONFIG['CLANG_CXX']:

--- a/gfx/angle/src/libANGLE/moz.build
+++ b/gfx/angle/src/libANGLE/moz.build
@@ -335,17 +335,17 @@ if CONFIG['MOZ_HAS_WINSDK_WITH_D3D']:
 if CONFIG['MOZ_HAS_WINSDK_WITH_D3D']:
     SOURCES += [
         'renderer/d3d/d3d11/SwapChain11.cpp',
         'renderer/d3d/d3d11/win32/NativeWindow11Win32.cpp',
     ]
 
 CXXFLAGS += CONFIG['SSE2_FLAGS']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += [
         '-Wno-attributes',
         '-Wno-shadow',
         '-Wno-sign-compare',
         '-Wno-unknown-pragmas',
         '-Wno-unreachable-code',
     ]
     if CONFIG['CLANG_CXX']:

--- a/gfx/angle/src/libEGL/moz.build
+++ b/gfx/angle/src/libEGL/moz.build
@@ -8,17 +8,17 @@
 #
 # WARNING WARNING WARNING
 #
 UNIFIED_SOURCES += [
     'libEGL.cpp',
 ]
 
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += [
         '-Wno-attributes',
         '-Wno-shadow',
         '-Wno-sign-compare',
         '-Wno-unknown-pragmas',
         '-Wno-unreachable-code',
     ]
     if CONFIG['CLANG_CXX']:

--- a/gfx/angle/src/libGLESv2/moz.build
+++ b/gfx/angle/src/libGLESv2/moz.build
@@ -15,17 +15,17 @@ UNIFIED_SOURCES += [
     'entry_points_gles_2_0_ext.cpp',
     'entry_points_gles_3_0_autogen.cpp',
     'entry_points_gles_3_1.cpp',
     'global_state.cpp',
     'libGLESv2.cpp',
 ]
 
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += [
         '-Wno-attributes',
         '-Wno-shadow',
         '-Wno-sign-compare',
         '-Wno-unknown-pragmas',
         '-Wno-unreachable-code',
     ]
     if CONFIG['CLANG_CXX']:

--- a/gfx/cairo/cairo/src/moz.build
+++ b/gfx/cairo/cairo/src/moz.build
@@ -188,17 +188,17 @@ DEFINES['PACKAGE_BUGREPORT'] = '"http://
 
 for var in ('CAIRO_HAS_PTHREAD', '_GNU_SOURCE'):
     DEFINES[var] = True
 
 for var in ('MOZ_TREE_CAIRO', 'MOZ_TREE_PIXMAN'):
     if CONFIG[var]:
         DEFINES[var] = True
 
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     DEFINES['HAVE_CXX11_ATOMIC_PRIMITIVES'] = True
     # We would normally use autoconf to set these up, using AC_CHECK_SIZEOF.
     # But AC_CHECK_SIZEOF requires running programs to determine the sizes,
     # and that doesn't work so well with cross-compiling.  So instead we
     # use these magic macros, available since at least GCC 4.3, to define
     # the preprocessor macros cairo wanted from autoconf.
     DEFINES['SIZEOF_VOID_P'] = '__SIZEOF_POINTER__'
     DEFINES['SIZEOF_INT'] = '__SIZEOF_INT__'
@@ -208,17 +208,17 @@ if CONFIG['GNU_CC']:
 # Normally determined by cairo's configure script.
 DEFINES['HAVE_UINT64_T'] = True
 
 if CONFIG['MOZ_TREE_FREETYPE']:
     DEFINES['HAVE_FT_LIBRARY_SETLCDFILTER'] = True
     DEFINES['FT_LCD_FILTER_H'] = '%s/modules/freetype2/include/freetype/ftlcdfil.h' % TOPSRCDIR
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC'] or CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']:
     CFLAGS += [
         '-Wno-enum-compare',
         '-Wno-int-to-pointer-cast',
         '-Wno-int-conversion',
         '-Wno-incompatible-pointer-types',
         '-Wno-sign-compare',
         '-Wno-type-limits',
         '-Wno-missing-field-initializers',
@@ -259,17 +259,17 @@ if CONFIG['_MSC_VER'] and not CONFIG['CL
         '-wd4005', # 'WIN32_LEAN_AND_MEAN' : macro redefinition
         '-wd4018', # '>' : signed/unsigned mismatch
         '-wd4146', # unary minus operator applied to unsigned type
         '-wd4828', # illegal in the current source character set
         '-wd4838', # requires a narrowing conversion
     ]
 
 # See bug 386897.
-if CONFIG['GNU_CC'] and CONFIG['OS_TARGET'] == 'Android' and CONFIG['MOZ_OPTIMIZE']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') and CONFIG['OS_TARGET'] == 'Android' and CONFIG['MOZ_OPTIMIZE']:
     CFLAGS += ['-O2']
     CXXFLAGS += ['-O2']
 
 if CONFIG['MOZ_X11']:
     CFLAGS += CONFIG['XCFLAGS']
 
 if CONFIG['MOZ_ENABLE_CAIRO_FT']:
     CFLAGS += CONFIG['CAIRO_FT_CFLAGS']

--- a/gfx/cairo/libpixman/src/moz.build
+++ b/gfx/cairo/libpixman/src/moz.build
@@ -8,17 +8,17 @@ EXPORTS += [
     'pixman-version.h',
     'pixman.h',
 ]
 
 # Apple's arm assembler doesn't support the same syntax as
 # the standard GNU assembler, so use the C fallback paths for now.
 # This may be fixable if clang's ARM/iOS assembler improves into a
 # viable solution in the future.
-if CONFIG['OS_ARCH'] != 'Darwin' and CONFIG['GNU_CC']:
+if CONFIG['OS_ARCH'] != 'Darwin' and CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     if CONFIG['HAVE_ARM_NEON']:
         SOURCES += [
             'pixman-arm-neon-asm-bilinear.S',
             'pixman-arm-neon-asm.S',
         ]
     if CONFIG['HAVE_ARM_SIMD']:
         SOURCES += [
             'pixman-arm-simd-asm-scaled.S',
@@ -82,49 +82,49 @@ use_sse2 = False
 use_vmx = False
 use_arm_simd_gcc = False
 use_arm_neon_gcc = False
 if '86' in CONFIG['OS_TEST']:
     use_sse2 = True
     if '64' not in CONFIG['OS_TEST']:
         if CONFIG['_MSC_VER']:
             use_mmx = True
-    if CONFIG['GNU_CC']:
+    if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         use_mmx = True
 elif 'ppc' in CONFIG['OS_TEST']:
-    if CONFIG['GNU_CC']:
+    if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         use_vmx = True
 # Apple's arm assembler doesn't support the same syntax as
 # the standard GNU assembler, so use the C fallback paths for now.
 # This may be fixable if clang's ARM/iOS assembler improves into a
 # viable solution in the future.
 elif 'arm' in CONFIG['OS_TEST']:
     if CONFIG['OS_ARCH'] != 'Darwin':
         if CONFIG['HAVE_ARM_SIMD']:
             use_arm_simd_gcc = True
         if CONFIG['HAVE_ARM_NEON']:
             use_arm_neon_gcc = True
 
 if use_mmx:
     DEFINES['USE_MMX'] = True
     SOURCES += ['pixman-mmx.c']
     SOURCES['pixman-mmx.c'].flags += CONFIG['MMX_FLAGS']
-    if CONFIG['GNU_CC']:
+    if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         SOURCES['pixman-mmx.c'].flags += [
             '-Winline',
             '--param', 'inline-unit-growth=10000',
             '--param', 'large-function-growth=10000',
         ]
 
 if use_sse2:
     DEFINES['USE_SSE'] = True
     DEFINES['USE_SSE2'] = True
     SOURCES += ['pixman-sse2.c']
     SOURCES['pixman-sse2.c'].flags += CONFIG['SSE_FLAGS'] + CONFIG['SSE2_FLAGS']
-    if CONFIG['GNU_CC']:
+    if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         SOURCES['pixman-sse2.c'].flags += ['-Winline']
 
 if use_vmx:
     DEFINES['USE_VMX'] = True
     SOURCES += ['pixman-vmx.c']
     SOURCES['pixman-vmx.c'].flags += ['-maltivec']
 
 if use_arm_simd_gcc:
@@ -132,17 +132,17 @@ if use_arm_simd_gcc:
     SOURCES += ['pixman-arm-simd.c']
 
 if use_arm_neon_gcc:
     DEFINES['USE_ARM_NEON'] = True
     SOURCES += ['pixman-arm-neon.c']
     SOURCES['pixman-arm-neon.c'].flags += CONFIG['NEON_FLAGS']
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC'] or CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']:
     CFLAGS += [
         '-Wno-address',
         '-Wno-missing-field-initializers',
         '-Wno-sign-compare',
         '-Wno-incompatible-pointer-types',
         '-Wno-unused',                      # too many unused warnings; ignore
     ]
 if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL']:

--- a/gfx/gl/moz.build
+++ b/gfx/gl/moz.build
@@ -153,10 +153,10 @@ if CONFIG['MOZ_D3DCOMPILER_VISTA_DLL']:
 
 CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 CXXFLAGS += CONFIG['TK_CFLAGS']
 CFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 CFLAGS += CONFIG['TK_CFLAGS']
 
 LOCAL_INCLUDES += CONFIG['SKIA_INCLUDES']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/gfx/graphite2/src/moz.build
+++ b/gfx/graphite2/src/moz.build
@@ -7,17 +7,17 @@
 # This should contain all of the _PUBLIC_HEADERS from files.mk
 EXPORTS.graphite2 += [
     '../include/graphite2/Font.h',
     '../include/graphite2/Log.h',
     '../include/graphite2/Segment.h',
     '../include/graphite2/Types.h',
 ]
 
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     UNIFIED_SOURCES += [
         'direct_machine.cpp'
     ]
 else:
     UNIFIED_SOURCES += [
         'call_machine.cpp'
     ]
 

--- a/gfx/layers/apz/test/gtest/moz.build
+++ b/gfx/layers/apz/test/gtest/moz.build
@@ -24,10 +24,10 @@ LOCAL_INCLUDES += [
     '/gfx/layers',
     '/gfx/tests/gtest'  # for TestLayers.h, which is shared with the gfx gtests
 ]
 
 FINAL_LIBRARY = 'xul-gtest'
 
 CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/gfx/layers/moz.build
+++ b/gfx/layers/moz.build
@@ -559,17 +559,17 @@ if CONFIG['ENABLE_TESTS']:
 MOCHITEST_MANIFESTS += ['apz/test/mochitest/mochitest.ini']
 MOCHITEST_CHROME_MANIFESTS += ['apz/test/mochitest/chrome.ini']
 
 CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 CXXFLAGS += CONFIG['TK_CFLAGS']
 
 LOCAL_INCLUDES += CONFIG['SKIA_INCLUDES']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
     # Suppress warnings in third-party code.
     CXXFLAGS += [
         '-Wno-maybe-uninitialized'
     ]
 
 if CONFIG['MOZ_ENABLE_SKIA']:
   UNIFIED_SOURCES += [

--- a/gfx/qcms/moz.build
+++ b/gfx/qcms/moz.build
@@ -14,17 +14,17 @@ SOURCES += [
     'iccread.c',
     'matrix.c',
     'transform.c',
     'transform_util.c',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CFLAGS += ['-Wno-missing-field-initializers']
 
 use_sse1 = False
 use_sse2 = False
 use_altivec = False
 if '86' in CONFIG['OS_TEST']:
     use_sse2 = True
     if CONFIG['_MSC_VER']:

--- a/gfx/skia/generate_mozbuild.py
+++ b/gfx/skia/generate_mozbuild.py
@@ -21,17 +21,17 @@ header = """
 # DO NOT MODIFY THIS FILE IT IS AUTOGENERATED.
 #
 
 skia_opt_flags = []
 
 if CONFIG['MOZ_OPTIMIZE']:
     if CONFIG['_MSC_VER']:
         skia_opt_flags += ['-O2']
-    elif CONFIG['GNU_CC']:
+    elif CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         skia_opt_flags += ['-O3']
 
 """
 
 footer = """
 
 # We allow warnings for third-party code that can be updated from upstream.
 ALLOW_COMPILER_WARNINGS = True
@@ -71,17 +71,17 @@ if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'wind
     DEFINES['_UNICODE'] = True
     UNIFIED_SOURCES += [
         'skia/src/fonts/SkFontMgr_indirect.cpp',
         'skia/src/fonts/SkRemotableFontMgr.cpp',
     ]
 
 # We should autogenerate these SSE related flags.
 
-if CONFIG['INTEL_ARCHITECTURE'] and (CONFIG['GNU_CC'] or CONFIG['CLANG_CL']):
+if CONFIG['INTEL_ARCHITECTURE'] and (CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']):
     SOURCES['skia/src/opts/SkBitmapProcState_opts_SSE2.cpp'].flags += CONFIG['SSE2_FLAGS']
     SOURCES['skia/src/opts/SkBitmapProcState_opts_SSSE3.cpp'].flags += ['-mssse3']
     SOURCES['skia/src/opts/SkBlitRow_opts_SSE2.cpp'].flags += CONFIG['SSE2_FLAGS']
     SOURCES['skia/src/opts/SkOpts_ssse3.cpp'].flags += ['-mssse3']
     SOURCES['skia/src/opts/SkOpts_sse41.cpp'].flags += ['-msse4.1']
     SOURCES['skia/src/opts/SkOpts_sse42.cpp'].flags += ['-msse4.2']
     SOURCES['skia/src/opts/SkOpts_avx.cpp'].flags += ['-mavx']
     SOURCES['skia/src/opts/SkOpts_hsw.cpp'].flags += ['-mavx2']
@@ -91,43 +91,43 @@ elif CONFIG['_MSC_VER']:
     SOURCES['skia/src/opts/SkBitmapProcState_opts_SSE2.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=20']
     SOURCES['skia/src/opts/SkBitmapProcState_opts_SSSE3.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=31']
     SOURCES['skia/src/opts/SkBlitRow_opts_SSE2.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=20']
     SOURCES['skia/src/opts/SkOpts_ssse3.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=31']
     SOURCES['skia/src/opts/SkOpts_sse41.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=41']
     SOURCES['skia/src/opts/SkOpts_sse42.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=42']
     SOURCES['skia/src/opts/SkOpts_avx.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=51']
     SOURCES['skia/src/opts/SkOpts_hsw.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=52']
-elif CONFIG['CPU_ARCH'] == 'arm' and CONFIG['GNU_CC']:
+elif CONFIG['CPU_ARCH'] == 'arm' and CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += CONFIG['NEON_FLAGS']
-elif CONFIG['CPU_ARCH'] == 'aarch64' and CONFIG['GNU_CC']:
+elif CONFIG['CPU_ARCH'] == 'aarch64' and CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     SOURCES['skia/src/opts/SkOpts_crc32.cpp'].flags += ['-march=armv8-a+crc']
 
 DEFINES['SKIA_IMPLEMENTATION'] = 1
 
 if CONFIG['MOZ_ENABLE_SKIA_PDF_SFNTLY']:
     DEFINES['SK_PDF_USE_SFNTLY'] = 1
 
 if not CONFIG['MOZ_ENABLE_SKIA_GPU']:
     DEFINES['SK_SUPPORT_GPU'] = 0
 
 if CONFIG['MOZ_TREE_FREETYPE']:
     DEFINES['SK_CAN_USE_DLOPEN'] = 0
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CXX'] or CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']:
     CXXFLAGS += [
         '-Wno-deprecated-declarations',
         '-Wno-overloaded-virtual',
         '-Wno-shadow',
         '-Wno-sign-compare',
         '-Wno-unreachable-code',
         '-Wno-unused-function',
     ]
-if CONFIG['GNU_CXX'] and not CONFIG['CLANG_CXX'] and not CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') and not CONFIG['CLANG_CXX'] and not CONFIG['CLANG_CL']:
     CXXFLAGS += [
         '-Wno-logical-op',
         '-Wno-maybe-uninitialized',
     ]
 if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL']:
     CXXFLAGS += [
         '-Wno-implicit-fallthrough',
         '-Wno-inconsistent-missing-override',
@@ -444,21 +444,21 @@ def write_mozbuild(sources):
   # Windows-specific files don't get unification because of nasty headers.
   # Luckily there are not many files in this.
   write_list(f, "SOURCES", sources['win'], 4)
 
   f.write("if CONFIG['INTEL_ARCHITECTURE']:\n")
   write_sources(f, sources['intel'], 4)
   write_cflags(f, sources['intel'], opt_whitelist, 'skia_opt_flags', 4)
 
-  f.write("elif CONFIG['CPU_ARCH'] == 'arm' and CONFIG['GNU_CC']:\n")
+  f.write("elif CONFIG['CPU_ARCH'] == 'arm' and CONFIG['CC_TYPE'] in ('clang', 'gcc'):\n")
   write_sources(f, sources['arm'], 4)
   write_cflags(f, sources['arm'], opt_whitelist, 'skia_opt_flags', 4)
 
-  f.write("elif CONFIG['CPU_ARCH'] == 'aarch64' and CONFIG['GNU_CC']:\n")
+  f.write("elif CONFIG['CPU_ARCH'] == 'aarch64' and CONFIG['CC_TYPE'] in ('clang', 'gcc'):\n")
   write_sources(f, sources['arm64'], 4)
   write_cflags(f, sources['arm64'], opt_whitelist, 'skia_opt_flags', 4)
 
   f.write("else:\n")
   write_sources(f, sources['none'], 4)
 
   f.write(footer)
 

--- a/gfx/skia/moz.build
+++ b/gfx/skia/moz.build
@@ -14,17 +14,17 @@
 # DO NOT MODIFY THIS FILE IT IS AUTOGENERATED.
 #
 
 skia_opt_flags = []
 
 if CONFIG['MOZ_OPTIMIZE']:
     if CONFIG['_MSC_VER']:
         skia_opt_flags += ['-O2']
-    elif CONFIG['GNU_CC']:
+    elif CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         skia_opt_flags += ['-O3']
 
 UNIFIED_SOURCES += [
     'skia/src/core/SkAAClip.cpp',
     'skia/src/core/SkAlphaRuns.cpp',
     'skia/src/core/SkAnalyticEdge.cpp',
     'skia/src/core/SkAnnotation.cpp',
     'skia/src/core/SkArenaAlloc.cpp',
@@ -629,34 +629,34 @@ if CONFIG['INTEL_ARCHITECTURE']:
     SOURCES['skia/src/opts/SkBitmapProcState_opts_SSE2.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkBitmapProcState_opts_SSSE3.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkBlitRow_opts_SSE2.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkOpts_avx.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkOpts_hsw.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkOpts_sse41.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkOpts_sse42.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkOpts_ssse3.cpp'].flags += skia_opt_flags
-elif CONFIG['CPU_ARCH'] == 'arm' and CONFIG['GNU_CC']:
+elif CONFIG['CPU_ARCH'] == 'arm' and CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     SOURCES += [
         'skia/src/opts/SkBitmapProcState_arm_neon.cpp',
         'skia/src/opts/SkBitmapProcState_matrixProcs_neon.cpp',
         'skia/src/opts/SkBitmapProcState_opts_none.cpp',
         'skia/src/opts/SkBlitMask_opts_arm.cpp',
         'skia/src/opts/SkBlitMask_opts_arm_neon.cpp',
         'skia/src/opts/SkBlitRow_opts_arm.cpp',
         'skia/src/opts/SkBlitRow_opts_arm_neon.cpp',
     ]
     SOURCES['skia/src/opts/SkBitmapProcState_arm_neon.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkBitmapProcState_matrixProcs_neon.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkBitmapProcState_opts_none.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkBlitMask_opts_arm.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkBlitMask_opts_arm_neon.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkBlitRow_opts_arm.cpp'].flags += skia_opt_flags
     SOURCES['skia/src/opts/SkBlitRow_opts_arm_neon.cpp'].flags += skia_opt_flags
-elif CONFIG['CPU_ARCH'] == 'aarch64' and CONFIG['GNU_CC']:
+elif CONFIG['CPU_ARCH'] == 'aarch64' and CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     SOURCES += [
         'skia/src/opts/SkBitmapProcState_arm_neon.cpp',
         'skia/src/opts/SkBitmapProcState_matrixProcs_neon.cpp',
         'skia/src/opts/SkBitmapProcState_opts_none.cpp',
         'skia/src/opts/SkBlitMask_opts_arm.cpp',
         'skia/src/opts/SkBlitMask_opts_arm_neon.cpp',
         'skia/src/opts/SkBlitRow_opts_arm.cpp',
         'skia/src/opts/SkBlitRow_opts_arm_neon.cpp',
@@ -716,17 +716,17 @@ if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'wind
     DEFINES['_UNICODE'] = True
     UNIFIED_SOURCES += [
         'skia/src/fonts/SkFontMgr_indirect.cpp',
         'skia/src/fonts/SkRemotableFontMgr.cpp',
     ]
 
 # We should autogenerate these SSE related flags.
 
-if CONFIG['INTEL_ARCHITECTURE'] and (CONFIG['GNU_CC'] or CONFIG['CLANG_CL']):
+if CONFIG['INTEL_ARCHITECTURE'] and (CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']):
     SOURCES['skia/src/opts/SkBitmapProcState_opts_SSE2.cpp'].flags += CONFIG['SSE2_FLAGS']
     SOURCES['skia/src/opts/SkBitmapProcState_opts_SSSE3.cpp'].flags += ['-mssse3']
     SOURCES['skia/src/opts/SkBlitRow_opts_SSE2.cpp'].flags += CONFIG['SSE2_FLAGS']
     SOURCES['skia/src/opts/SkOpts_ssse3.cpp'].flags += ['-mssse3']
     SOURCES['skia/src/opts/SkOpts_sse41.cpp'].flags += ['-msse4.1']
     SOURCES['skia/src/opts/SkOpts_sse42.cpp'].flags += ['-msse4.2']
     SOURCES['skia/src/opts/SkOpts_avx.cpp'].flags += ['-mavx']
     SOURCES['skia/src/opts/SkOpts_hsw.cpp'].flags += ['-mavx2']
@@ -736,43 +736,43 @@ elif CONFIG['_MSC_VER']:
     SOURCES['skia/src/opts/SkBitmapProcState_opts_SSE2.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=20']
     SOURCES['skia/src/opts/SkBitmapProcState_opts_SSSE3.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=31']
     SOURCES['skia/src/opts/SkBlitRow_opts_SSE2.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=20']
     SOURCES['skia/src/opts/SkOpts_ssse3.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=31']
     SOURCES['skia/src/opts/SkOpts_sse41.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=41']
     SOURCES['skia/src/opts/SkOpts_sse42.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=42']
     SOURCES['skia/src/opts/SkOpts_avx.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=51']
     SOURCES['skia/src/opts/SkOpts_hsw.cpp'].flags += ['-DSK_CPU_SSE_LEVEL=52']
-elif CONFIG['CPU_ARCH'] == 'arm' and CONFIG['GNU_CC']:
+elif CONFIG['CPU_ARCH'] == 'arm' and CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += CONFIG['NEON_FLAGS']
-elif CONFIG['CPU_ARCH'] == 'aarch64' and CONFIG['GNU_CC']:
+elif CONFIG['CPU_ARCH'] == 'aarch64' and CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     SOURCES['skia/src/opts/SkOpts_crc32.cpp'].flags += ['-march=armv8-a+crc']
 
 DEFINES['SKIA_IMPLEMENTATION'] = 1
 
 if CONFIG['MOZ_ENABLE_SKIA_PDF_SFNTLY']:
     DEFINES['SK_PDF_USE_SFNTLY'] = 1
 
 if not CONFIG['MOZ_ENABLE_SKIA_GPU']:
     DEFINES['SK_SUPPORT_GPU'] = 0
 
 if CONFIG['MOZ_TREE_FREETYPE']:
     DEFINES['SK_CAN_USE_DLOPEN'] = 0
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CXX'] or CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']:
     CXXFLAGS += [
         '-Wno-deprecated-declarations',
         '-Wno-overloaded-virtual',
         '-Wno-shadow',
         '-Wno-sign-compare',
         '-Wno-unreachable-code',
         '-Wno-unused-function',
     ]
-if CONFIG['GNU_CXX'] and not CONFIG['CLANG_CXX'] and not CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') and not CONFIG['CLANG_CXX'] and not CONFIG['CLANG_CL']:
     CXXFLAGS += [
         '-Wno-logical-op',
         '-Wno-maybe-uninitialized',
     ]
 if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL']:
     CXXFLAGS += [
         '-Wno-implicit-fallthrough',
         '-Wno-inconsistent-missing-override',

--- a/gfx/tests/gtest/moz.build
+++ b/gfx/tests/gtest/moz.build
@@ -59,10 +59,10 @@ LOCAL_INCLUDES += [
     '/gfx/ots/src',
     '/gfx/qcms',
 ]
 
 FINAL_LIBRARY = 'xul-gtest'
 
 CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/gfx/vr/openvr/moz.build
+++ b/gfx/vr/openvr/moz.build
@@ -12,17 +12,17 @@ if CONFIG['OS_ARCH'] == 'WINNT':
     if CONFIG['HAVE_64BIT_BUILD']:
         DEFINES['WIN64'] = True
     else:
         DEFINES['WIN32'] = True
 
 if CONFIG['OS_ARCH'] == 'Darwin':
     DEFINES['POSIX'] = True
     DEFINES['OSX'] = True
-    if CONFIG['GNU_CXX']:
+    if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         CXXFLAGS += ['-xobjective-c++']
 
 if CONFIG['OS_ARCH'] == 'Linux':
     DEFINES['POSIX'] = True
     DEFINES['LINUX'] = True
     if CONFIG['HAVE_64BIT_BUILD']:
         DEFINES['LINUX64'] = True
     else:
@@ -46,14 +46,14 @@ SOURCES += [
     'src/hmderrors_public.cpp',
     'src/openvr_api_public.cpp',
     'src/pathtools_public.cpp',
     'src/sharedlibtools_public.cpp',
     'src/strtools_public.cpp',
     'src/vrpathregistry_public.cpp',
 ]
 
-if CONFIG['CLANG_CXX'] or CONFIG['GNU_CXX']:
+if CONFIG['CLANG_CXX'] or CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     # Harmless warnings in 3rd party code
     CXXFLAGS += [
         '-Wno-error=parentheses',
         '-Wno-error=unused-variable',
     ]

--- a/image/decoders/moz.build
+++ b/image/decoders/moz.build
@@ -38,10 +38,10 @@ LOCAL_INCLUDES += [
     # Decoders need ImageLib headers.
     '/image',
 ]
 
 LOCAL_INCLUDES += CONFIG['SKIA_INCLUDES']
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/image/moz.build
+++ b/image/moz.build
@@ -108,16 +108,16 @@ LOCAL_INCLUDES += [
     '/xpcom/threads',
 ]
 
 # Because imgFrame.cpp includes "cairo.h"
 CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 
 LOCAL_INCLUDES += CONFIG['SKIA_INCLUDES']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 if CONFIG['FUZZING']:
     if CONFIG['LIBFUZZER']:
         # Add trace-pc coverage for libfuzzer
         CFLAGS += ['-fsanitize-coverage=trace-pc-guard']
         CXXFLAGS += ['-fsanitize-coverage=trace-pc-guard']

--- a/image/test/gtest/moz.build
+++ b/image/test/gtest/moz.build
@@ -74,10 +74,10 @@ LOCAL_INCLUDES += [
     '/gfx/2d',
     '/image',
 ]
 
 LOCAL_INCLUDES += CONFIG['SKIA_INCLUDES']
 
 FINAL_LIBRARY = 'xul-gtest'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/intl/hyphenation/glue/moz.build
+++ b/intl/hyphenation/glue/moz.build
@@ -20,10 +20,10 @@ SOURCES += [
 ]
 
 LOCAL_INCLUDES += [
     '../hyphen',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/intl/strres/moz.build
+++ b/intl/strres/moz.build
@@ -15,10 +15,10 @@ XPIDL_MODULE = 'intl'
 
 UNIFIED_SOURCES += [
     'nsStringBundle.cpp',
     'nsStringBundleTextOverride.cpp',
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/intl/uconv/moz.build
+++ b/intl/uconv/moz.build
@@ -24,10 +24,10 @@ UNIFIED_SOURCES += [
     'nsScriptableUConv.cpp',
     'nsTextToSubURI.cpp',
     'nsUConvModule.cpp',
     'nsUTF8ConverterService.cpp'
 ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/ipc/app/moz.build
+++ b/ipc/app/moz.build
@@ -71,18 +71,18 @@ if CONFIG['_MSC_VER']:
 # Control the default heap size.
 # This is the heap returned by GetProcessHeap().
 # As we use the CRT heap, the default size is too large and wastes VM.
 #
 # The default heap size is 1MB on Win32.
 # The heap will grow if need be.
 #
 # Set it to 256k.  See bug 127069.
-if CONFIG['OS_ARCH'] == 'WINNT' and not CONFIG['GNU_CC']:
+if CONFIG['OS_ARCH'] == 'WINNT' and CONFIG['CC_TYPE'] not in ('clang', 'gcc'):
     LDFLAGS += ['/HEAP:0x40000']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wshadow']
 
 DEFINES['MOZ_PLUGIN_CONTAINER'] = 1;
 
 with Files("**"):
     BUG_COMPONENT = ("Core", "DOM: Content Processes")

--- a/ipc/chromium/moz.build
+++ b/ipc/chromium/moz.build
@@ -150,10 +150,10 @@ CXXFLAGS += CONFIG['TK_CFLAGS']
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
 DIRS += [
     'atomics',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/ipc/glue/moz.build
+++ b/ipc/glue/moz.build
@@ -224,10 +224,10 @@ for var in ('MOZ_CHILD_PROCESS_NAME', 'M
 
 if CONFIG['MOZ_SANDBOX'] and CONFIG['OS_ARCH'] == 'WINNT':
     LOCAL_INCLUDES += [
         '/security/sandbox/chromium',
         '/security/sandbox/chromium-shim',
         '/security/sandbox/win/src/sandboxbroker',
     ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-shadow']

--- a/ipc/testshell/moz.build
+++ b/ipc/testshell/moz.build
@@ -28,13 +28,13 @@ include('/ipc/chromium/chromium-config.m
 FINAL_LIBRARY = 'xul'
 
 # For xpcshell error messages and nsAutoJSString
 LOCAL_INCLUDES += [
     '/dom/base',
     '/js/xpconnect/src',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 with Files("**"):
     BUG_COMPONENT = ("Core", "XPConnect")

--- a/js/ipc/moz.build
+++ b/js/ipc/moz.build
@@ -32,10 +32,10 @@ EXPORTS.mozilla.jsipc = [
 LOCAL_INCLUDES += [
     '/dom/base',
     '/js/ipc',
     '/js/src',
     '/js/xpconnect/src',
     '/js/xpconnect/wrappers',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-shadow']

--- a/js/src/gdb/moz.build
+++ b/js/src/gdb/moz.build
@@ -36,17 +36,17 @@ USE_LIBS += [
 
 if CONFIG['ENABLE_INTL_API'] and CONFIG['MOZ_ICU_DATA_ARCHIVE']:
     # The ICU libraries linked into libmozjs will not include the ICU data,
     # so link it directly.
     USE_LIBS += ['icudata']
 
 OS_LIBS += CONFIG['MOZ_ZLIB_LIBS']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-shadow', '-fno-strict-aliasing']
 
 # This is intended as a temporary workaround to enable VS2015.
 if CONFIG['_MSC_VER']:
     CXXFLAGS += ['-wd4312']
 
 DEFINES['topsrcdir'] = '%s/js/src' % TOPSRCDIR
 FINAL_TARGET_PP_FILES += ['gdb-tests-gdb.py.in']

--- a/js/src/jsapi-tests/moz.build
+++ b/js/src/jsapi-tests/moz.build
@@ -153,17 +153,17 @@ USE_LIBS += [
     'static:js',
 ]
 
 if CONFIG['MOZ_NEEDS_LIBATOMIC']:
     OS_LIBS += ['atomic']
 
 OS_LIBS += CONFIG['MOZ_ZLIB_LIBS']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-shadow', '-Werror=format', '-fno-strict-aliasing']
 
 # This is intended as a temporary workaround to enable VS2015.
 if CONFIG['_MSC_VER']:
     CXXFLAGS += ['-wd4312']
 
 DEFINES['topsrcdir'] = '%s/js/src' % TOPSRCDIR
 OBJDIR_PP_FILES.js.src['jsapi-tests'] += ['jsapi-tests-gdb.py.in']

--- a/js/src/moz.build
+++ b/js/src/moz.build
@@ -734,23 +734,23 @@ selfhosted.inputs = [
 
 if CONFIG['JS_HAS_CTYPES']:
     if CONFIG['MOZ_SYSTEM_FFI']:
         CXXFLAGS += CONFIG['MOZ_FFI_CFLAGS']
     else:
         # Windows needs this to be linked with a static library.
         DEFINES['FFI_BUILDING'] = True
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     # Also disable strict-aliasing for GCC compiler, that is enabled by default
     # starting with version 7.1, see Bug 1363009
     CXXFLAGS += ['-Wno-shadow', '-Werror=format', '-fno-strict-aliasing']
 
 # Suppress warnings in third-party code.
-if CONFIG['CLANG_CXX'] or CONFIG['GNU_CXX']:
+if CONFIG['CLANG_CXX'] or CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     SOURCES['jsdtoa.cpp'].flags += ['-Wno-implicit-fallthrough']
 
 # Generate GC statistics phase data.
 GENERATED_FILES += ['gc/StatsPhasesGenerated.h']
 StatsPhasesGeneratedHeader = GENERATED_FILES['gc/StatsPhasesGenerated.h']
 StatsPhasesGeneratedHeader.script = 'gc/GenerateStatsPhases.py:generateHeader'
 GENERATED_FILES += ['gc/StatsPhasesGenerated.cpp']
 StatsPhasesGeneratedCpp = GENERATED_FILES['gc/StatsPhasesGenerated.cpp']

--- a/js/src/shell/moz.build
+++ b/js/src/shell/moz.build
@@ -45,17 +45,17 @@ if CONFIG['ENABLE_INTL_API'] and CONFIG[
 GENERATED_FILES += ['shellmoduleloader.out.h']
 shellmoduleloader = GENERATED_FILES['shellmoduleloader.out.h']
 shellmoduleloader.script = '../builtin/embedjs.py:generate_shellmoduleloader'
 shellmoduleloader.inputs = [
     '../js.msg',
     'ModuleLoader.js',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-shadow', '-Werror=format']
 
 # This is intended as a temporary workaround to enable VS2015.
 if CONFIG['_MSC_VER']:
     CXXFLAGS += ['-wd4312']
 
 # Place a GDB Python auto-load file next to the shell executable, both in
 # the build directory and in the dist/bin directory.

--- a/js/xpconnect/loader/moz.build
+++ b/js/xpconnect/loader/moz.build
@@ -47,10 +47,10 @@ FINAL_LIBRARY = 'xul'
 LOCAL_INCLUDES += [
     '../src',
     '../wrappers',
     '/dom/base',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-shadow']

--- a/js/xpconnect/src/moz.build
+++ b/js/xpconnect/src/moz.build
@@ -57,10 +57,10 @@ LOCAL_INCLUDES += [
     '/dom/html',
     '/dom/svg',
     '/dom/workers',
     '/layout/base',
     '/layout/style',
     '/xpcom/reflect/xptinfo',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-shadow', '-Werror=format']

--- a/js/xpconnect/wrappers/moz.build
+++ b/js/xpconnect/wrappers/moz.build
@@ -33,10 +33,10 @@ include('/ipc/chromium/chromium-config.m
 FINAL_LIBRARY = 'xul'
 
 LOCAL_INCLUDES += [
     '../../../dom/base',
     '../src',
     '/caps',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-shadow']

--- a/layout/base/moz.build
+++ b/layout/base/moz.build
@@ -167,10 +167,10 @@ MARIONETTE_LAYOUT_MANIFESTS += ['tests/m
 MOCHITEST_MANIFESTS += ['tests/mochitest.ini']
 MOCHITEST_CHROME_MANIFESTS += ['tests/chrome/chrome.ini']
 
 if CONFIG['_MSC_VER']:
     # This is intended as a temporary hack to support building with VS2015.
     # 'type cast': conversion from 'unsigned int' to 'void *' of greater size
     CXXFLAGS += ['-wd4312']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/layout/build/moz.build
+++ b/layout/build/moz.build
@@ -82,10 +82,10 @@ if CONFIG['MOZ_WEBSPEECH']:
 
 if CONFIG['MOZ_SECUREELEMENT']:
     LOCAL_INCLUDES += [
         '/dom/secureelement',
     ]
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/layout/forms/moz.build
+++ b/layout/forms/moz.build
@@ -49,10 +49,10 @@ LOCAL_INCLUDES += [
     '../generic',
     '../painting',
     '../style',
     '../xul',
     '/dom/base',
     '/dom/html',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/layout/generic/moz.build
+++ b/layout/generic/moz.build
@@ -219,10 +219,10 @@ RESOURCE_FILES.html = [
 MOCHITEST_MANIFESTS += ['test/mochitest.ini']
 MOCHITEST_CHROME_MANIFESTS += ['test/chrome.ini']
 
 CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 
 if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     CXXFLAGS += CONFIG['TK_CFLAGS']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/layout/mathml/moz.build
+++ b/layout/mathml/moz.build
@@ -59,10 +59,10 @@ LOCAL_INCLUDES += [
 JAR_MANIFESTS += ['jar.mn']
 
 RESOURCE_FILES.fonts += [
     'mathfont.properties',
     'mathfontSTIXGeneral.properties',
     'mathfontUnicode.properties',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/layout/painting/moz.build
+++ b/layout/painting/moz.build
@@ -67,10 +67,10 @@ FINAL_LIBRARY = 'xul'
 
 CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 
 if CONFIG['_MSC_VER']:
     # This is intended as a temporary hack to support building with VS2015.
     # 'type cast': conversion from 'unsigned int' to 'void *' of greater size
     CXXFLAGS += ['-wd4312']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/layout/tables/moz.build
+++ b/layout/tables/moz.build
@@ -47,10 +47,10 @@ LOCAL_INCLUDES += [
     '../style',
     '../xul',
     '/dom/base',
     '/dom/html',
 ]
 
 DEFINES['DEBUG_TABLE_STRATEGY_off'] = True
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/layout/xul/grid/moz.build
+++ b/layout/xul/grid/moz.build
@@ -34,10 +34,10 @@ UNIFIED_SOURCES += [
 FINAL_LIBRARY = 'xul'
 LOCAL_INCLUDES += [
     '..',
     '../../forms',
     '../../generic',
     '../../style',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/layout/xul/moz.build
+++ b/layout/xul/moz.build
@@ -101,10 +101,10 @@ LOCAL_INCLUDES += [
     '../base',
     '../generic',
     '../painting',
     '../style',
     '/dom/base',
     '/dom/xul',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/layout/xul/tree/moz.build
+++ b/layout/xul/tree/moz.build
@@ -46,10 +46,10 @@ LOCAL_INCLUDES += [
     '../../forms',
     '../../generic',
     '../../painting',
     '../../style',
     '/dom/base',
     '/dom/xul',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/media/ffvpx/ffvpxcommon.mozbuild
+++ b/media/ffvpx/ffvpxcommon.mozbuild
@@ -45,17 +45,17 @@ if CONFIG['FFVPX_ASFLAGS']:
 
 
 LOCAL_INCLUDES += ['/media/ffvpx']
 
 # We allow warnings for third-party code that can be updated from upstream.
 AllowCompilerWarnings()
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CFLAGS += [
         '-Wno-parentheses',
         '-Wno-pointer-sign',
         '-Wno-sign-compare',
         '-Wno-switch',
         '-Wno-type-limits',
         '-Wno-unused-function',
         # XXX This does not seem to have any effect on some versions of GCC.

--- a/media/gmp-clearkey/0.1/moz.build
+++ b/media/gmp-clearkey/0.1/moz.build
@@ -53,17 +53,17 @@ TEST_DIRS += [
 ]
 
 DisableStlWrapping()
 DEFINES['MOZ_NO_MOZALLOC'] = True
 
 USE_LIBS += ['psshparser']
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CFLAGS += [
         '-Wno-missing-braces',
         '-Wno-pointer-to-int-cast',
         '-Wno-sign-compare',
         '-include', 'stdio.h',      # for sprintf() prototype
         '-include', 'unistd.h',     # for getpid() prototype
     ]
 elif CONFIG['_MSC_VER']:

--- a/media/libaom/moz.build
+++ b/media/libaom/moz.build
@@ -113,17 +113,17 @@ if CONFIG['CLANG_CL'] or not CONFIG['_MS
 if CONFIG['_MSC_VER'] and not CONFIG['CLANG_CL']:
     for f in SOURCES:
         if f.endswith('avx.c'):
             SOURCES[f].flags += ['-arch:AVX']
         if f.endswith('avx2.c'):
             SOURCES[f].flags += ['-arch:AVX2']
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC'] or CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']:
     CFLAGS += [
         '-Wno-sign-compare',
         '-Wno-unused-function', # so many of these warnings; just ignore them
     ]
 if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL']:
     CFLAGS += [
         '-Wno-unreachable-code',
         '-Wno-unneeded-internal-declaration',

--- a/media/libav/libavcommon.mozbuild
+++ b/media/libav/libavcommon.mozbuild
@@ -23,17 +23,17 @@ elif CONFIG['OS_ARCH'] == 'Darwin':
     ASFLAGS += ['-Pconfig_darwin.asm', '-DPREFIX']
 else:
     # Default to unix, similar to how ASFLAGS setup works in configure.in
     ASFLAGS += ['-Pconfig_unix.asm']
 
 LOCAL_INCLUDES += ['/media/libav']
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC'] or CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']:
     CFLAGS += [
         '-Wno-parentheses',
         '-Wno-pointer-sign',
         '-Wno-sign-compare',
         '-Wno-switch',
         '-Wno-type-limits',
     ]
 if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL']:

--- a/media/libcubeb/gtest/moz.build
+++ b/media/libcubeb/gtest/moz.build
@@ -70,12 +70,12 @@ elif CONFIG['MOZ_WIDGET_TOOLKIT'] == 'ui
 elif CONFIG['OS_TARGET'] == 'OpenBSD':
     OS_LIBS += [
         'sndio',
     ]
 else:
     OS_LIBS += CONFIG['MOZ_ALSA_LIBS']
     OS_LIBS += CONFIG['MOZ_PULSEAUDIO_LIBS']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 FINAL_LIBRARY = 'xul-gtest'

--- a/media/libopus/moz.build
+++ b/media/libopus/moz.build
@@ -40,17 +40,17 @@ if CONFIG['MOZ_DEBUG']:
     DEFINES['ENABLE_ASSERTIONS'] = True
 
 if CONFIG['OS_ARCH'] in ('Linux', 'Darwin', 'DragonFly', 'FreeBSD',
                          'NetBSD', 'OpenBSD'):
     DEFINES['HAVE_LRINTF'] = True
 
 if CONFIG['OS_ARCH'] == 'WINNT':
     DEFINES['inline'] = '__inline'
-    if CONFIG['GNU_CC']:
+    if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         DEFINES['HAVE_LRINTF'] = True
 
 if CONFIG['OS_ARCH'] == 'AIX':
     DEFINES['alloca'] = '__alloca'
 
 if CONFIG['OS_ARCH'] == 'SunOS':
     DEFINES['HAVE_ALLOCA_H'] = True
 
@@ -125,11 +125,11 @@ if CONFIG['CPU_ARCH'] == 'arm' and CONFI
     # These flags are a lie; they're just used to enable the requisite
     # opcodes; actual arch detection is done at runtime.
     ASFLAGS += [
         '-march=armv7-a',
     ]
     ASFLAGS += CONFIG['NEON_FLAGS']
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     if CONFIG['CLANG_CXX']:
         CFLAGS += ['-Wno-#pragma-messages']

--- a/media/libpng/moz.build
+++ b/media/libpng/moz.build
@@ -60,10 +60,10 @@ if CONFIG['MOZ_TREE_FREETYPE']:
 
 Library('mozpng')
 
 FINAL_LIBRARY = 'gkmedias'
 
 # We allow warnings for third-party code that can be updated from upstream.
 AllowCompilerWarnings()
 
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CFLAGS += ['-std=c89']

--- a/media/libspeex_resampler/src/moz.build
+++ b/media/libspeex_resampler/src/moz.build
@@ -42,16 +42,16 @@ if CONFIG['INTEL_ARCHITECTURE'] and not 
 if CONFIG['CPU_ARCH'] == 'arm' and CONFIG['BUILD_ARM_NEON']:
     DEFINES['_USE_NEON'] = True
     SOURCES += [
         'resample_neon.c'
     ]
     SOURCES['resample_neon.c'].flags += CONFIG['NEON_FLAGS']
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CFLAGS += ['-Wno-sign-compare']
 
 if CONFIG['_MSC_VER'] and not CONFIG['CLANG_CL']:
     CFLAGS += [
         '-wd4018', # '<' : signed/unsigned mismatch
         '-wd4101', # unreferenced local variable
     ]

--- a/media/libtheora/moz.build
+++ b/media/libtheora/moz.build
@@ -17,17 +17,17 @@ EXPORTS.theora += [
 AllowCompilerWarnings()
 
 FINAL_LIBRARY = 'gkmedias'
 
 # The encoder is currently not included.
 DEFINES['THEORA_DISABLE_ENCODE'] = True
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC'] or CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']:
     CFLAGS += ['-Wno-type-limits']
 if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL']:
     CFLAGS += ['-Wno-tautological-compare']
 if CONFIG['CLANG_CL']:
     CFLAGS += [
         '-Wno-pointer-sign',
         '-Wno-shift-op-parentheses',
     ]

--- a/media/libtremor/lib/moz.build
+++ b/media/libtremor/lib/moz.build
@@ -19,17 +19,17 @@ SOURCES += [
     'tremor_window.c',
 ]
 
 FINAL_LIBRARY = 'gkmedias'
 
 if CONFIG['OS_ARCH'] == 'AIX':
     DEFINES['alloca'] = '__alloca'
 
-if CONFIG['TARGET_CPU'] == 'arm' and CONFIG['GNU_CC'] and not CONFIG['MOZ_THUMB2']:
+if CONFIG['TARGET_CPU'] == 'arm' and CONFIG['CC_TYPE'] in ('clang', 'gcc') and not CONFIG['MOZ_THUMB2']:
     DEFINES['_ARM_ASSEM_'] = True
 
 LOCAL_INCLUDES += [
     '/media/libtremor/include/tremor',
 ]
 
 # We allow warnings for third-party code that can be updated from upstream.
 AllowCompilerWarnings()

--- a/media/libvorbis/moz.build
+++ b/media/libvorbis/moz.build
@@ -49,10 +49,10 @@ if CONFIG['OS_ARCH'] == 'SunOS':
     DEFINES['HAVE_ALLOCA_H'] = True
 
 # We allow warnings for third-party code that can be updated from upstream.
 AllowCompilerWarnings()
 
 FINAL_LIBRARY = 'gkmedias'
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CFLAGS += ['-Wno-uninitialized']

--- a/media/libvpx/moz.build
+++ b/media/libvpx/moz.build
@@ -112,17 +112,17 @@ if CONFIG['_MSC_VER'] and not CONFIG['CL
     for f in SOURCES:
         if f.endswith('.c'):
             if 'avx.c' in f:
                 SOURCES[f].flags += ['-arch:AVX']
             if 'avx2.c' in f:
                 SOURCES[f].flags += ['-arch:AVX2']
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC'] or CONFIG['CLANG_CL']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc') or CONFIG['CLANG_CL']:
     CFLAGS += [
         '-Wno-sign-compare',
         '-Wno-unused-function', # so many of these warnings; just ignore them
     ]
 if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL']:
     CFLAGS += [
         '-Wno-unreachable-code',
         '-Wno-unneeded-internal-declaration',

--- a/media/mtransport/common.build
+++ b/media/mtransport/common.build
@@ -82,10 +82,10 @@ for var in ('HAVE_STRDUP', 'NR_SOCKET_IS
 
 DEFINES['R_DEFINED_INT2'] = 'int16_t'
 DEFINES['R_DEFINED_UINT2'] = 'uint16_t'
 DEFINES['R_DEFINED_INT4'] = 'int32_t'
 DEFINES['R_DEFINED_UINT4'] = 'uint32_t'
 DEFINES['R_DEFINED_INT8'] = 'int64_t'
 DEFINES['R_DEFINED_UINT8'] = 'uint64_t'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/media/mtransport/test/moz.build
+++ b/media/mtransport/test/moz.build
@@ -90,10 +90,10 @@ LOCAL_INCLUDES += [
     '/media/mtransport/third_party/nrappkit/src/util/',
     '/media/mtransport/third_party/nrappkit/src/util/libekr',
     '/netwerk/sctp/src/',
     '/xpcom/tests/'
 ]
 
 FINAL_LIBRARY = 'xul-gtest'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/media/sphinxbase/moz.build
+++ b/media/sphinxbase/moz.build
@@ -64,22 +64,22 @@ SOURCES += [
     'src/libsphinxbase/util/sbthread.c',
     'src/libsphinxbase/util/slamch.c',
     'src/libsphinxbase/util/slapack_lite.c',
     'src/libsphinxbase/util/strfuncs.c',
     'src/libsphinxbase/util/utf8.c',
 ]
 
 # Suppress warnings in third-party code.
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CFLAGS += [
         '-Wno-parentheses',
         '-Wno-sign-compare',
     ]
 
 # Add define required of third party code.
-if CONFIG['GNU_CC']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     DEFINES['HAVE_CONFIG_H'] = True
 
 # We allow warnings for third-party code that can be updated from upstream.
 AllowCompilerWarnings()
 
 FINAL_LIBRARY = 'gkmedias'

--- a/media/webrtc/trunk/gtest/moz.build
+++ b/media/webrtc/trunk/gtest/moz.build
@@ -551,17 +551,17 @@ if CONFIG['OS_TARGET'] in ['Darwin', 'Li
         '../webrtc/modules/video_coding/video_codec_initializer_unittest.cc',
         '../webrtc/test/rtp_file_writer.cc',
         '../webrtc/test/testsupport/frame_writer_unittest.cc',
         '../webrtc/video/overuse_frame_detector_unittest.cc',
         '../webrtc/voice_engine/voe_codec_unittest.cc',
         '../webrtc/voice_engine/voice_engine_fixture.cc',
     ]
 
-    if CONFIG['GNU_CXX']:
+    if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         CXXFLAGS += [
             '-Wno-inconsistent-missing-override',
             '-Wno-overloaded-virtual',
         ]
         if CONFIG['CLANG_CXX']:
             CXXFLAGS += ['-Wno-comma']
 
     if CONFIG['_MSC_VER']:

--- a/media/webrtc/webrtc.mozbuild
+++ b/media/webrtc/webrtc.mozbuild
@@ -16,10 +16,10 @@ if CONFIG['MOZ_WEBRTC']:
     elif CONFIG['OS_TARGET'] == 'WINNT':
         DEFINES['WEBRTC_WIN'] = True
         DEFINES['HAVE_WINSOCK2_H'] = True
     elif CONFIG['OS_TARGET'] in ('DragonFly', 'FreeBSD', 'NetBSD', 'OpenBSD'):
         DEFINES['WEBRTC_BSD'] = True
     elif CONFIG['OS_TARGET'] == 'Android':
         DEFINES['WEBRTC_ANDROID'] = True
 
-    if CONFIG['GNU_CXX']:
+    if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         CXXFLAGS += ['-Wno-error=shadow']

--- a/memory/mozalloc/moz.build
+++ b/memory/mozalloc/moz.build
@@ -7,17 +7,17 @@ NoVisibilityFlags()
 
 EXPORTS.mozilla += [
     'mozalloc.h',
     'mozalloc_abort.h',
     'mozalloc_oom.h',
 ]
 
 if CONFIG['WRAP_STL_INCLUDES']:
-    if CONFIG['GNU_CXX']:
+    if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
         EXPORTS.mozilla += ['throw_gcc.h']
     elif CONFIG['_MSC_VER']:
         DEFINES['_HAS_EXCEPTIONS'] = 0
         if CONFIG['MOZ_MSVC_STL_WRAP_RAISE']:
             SOURCES += [
                 'msvc_raise_wrappers.cpp',
             ]
 

--- a/memory/replace/dmd/test/moz.build
+++ b/memory/replace/dmd/test/moz.build
@@ -17,10 +17,10 @@ else:
 DEFINES['MOZ_NO_MOZALLOC'] = True
 
 DisableStlWrapping()
 
 XPCSHELL_TESTS_MANIFESTS += [
     'xpcshell.ini',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/mfbt/tests/moz.build
+++ b/mfbt/tests/moz.build
@@ -76,10 +76,10 @@ if CONFIG['_MSC_VER']:
     '-wd4275', # non dll-interface class used as base for dll-interface class
     '-wd4530', # C++ exception handler used, but unwind semantics are not enabled
   ]
 
 USE_LIBS += [
     'mfbt',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']

--- a/modules/fdlibm/src/moz.build
+++ b/modules/fdlibm/src/moz.build
@@ -5,17 +5,17 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 EXPORTS += [
     'fdlibm.h',
 ]
 
 FINAL_LIBRARY = 'js'
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += [
         '-Wno-parentheses',
         '-Wno-sign-compare',
     ]
 
 if CONFIG['CLANG_CXX']:
     CXXFLAGS += [
         '-Wno-dangling-else',

--- a/modules/libpref/test/gtest/moz.build
+++ b/modules/libpref/test/gtest/moz.build
@@ -9,17 +9,17 @@ Library('libpreftests')
 LOCAL_INCLUDES += [
     '../..',
 ]
 
 UNIFIED_SOURCES = [
     'CallbackAndVarCacheOrder.cpp',
 ]
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 # THE MOCK_METHOD2 macro from gtest triggers this clang warning and it's hard
 # to work around, so we just ignore it.
 if CONFIG['CLANG_CXX']:
   CXXFLAGS += ['-Wno-inconsistent-missing-override']
   # Workaround bug 1142396. Suppress the warning from gmock library for clang.
   CXXFLAGS += ['-Wno-null-dereference']

--- a/mozglue/android/moz.build
+++ b/mozglue/android/moz.build
@@ -49,16 +49,16 @@ LOCAL_INCLUDES += [
     '/security/nss/lib/ssl',
     '/security/nss/lib/util',
     '/toolkit/components/startup',
     '/xpcom/build',
 ]
 
 DisableStlWrapping()
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 DEFINES['XPCOM_GLUE'] = True
 
 USE_LIBS += [
     'xpcomglue',
 ]

--- a/mozglue/linker/moz.build
+++ b/mozglue/linker/moz.build
@@ -18,16 +18,16 @@ Library('linker')
 FINAL_LIBRARY = 'mozglue'
 
 DEFINES['IMPL_MFBT'] = True
 
 DisableStlWrapping()
 
 TEST_DIRS += ['tests']
 
-if CONFIG['GNU_CXX']:
+if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     CXXFLAGS += ['-Wno-error=shadow']
 
 DEFINES['XZ_USE_CRC64'] = 1
 
 USE_LIBS += [
     'xz-embedded',
 ]