--- a/browser/config/mozconfigs/linux32/l10n-mozconfig
+++ b/browser/config/mozconfigs/linux32/l10n-mozconfig
@@ -9,15 +9,13 @@ if test `uname -m` = "x86_64"; then
   ac_add_options --host=i686-pc-linux
 fi
 
 export MOZILLA_OFFICIAL=1
 
 # Enable Telemetry
 export MOZ_TELEMETRY_REPORTING=1
 
-ac_add_options --disable-stdcxx-compat
-
 # Don't autoclobber l10n, as this can lead to missing binaries and broken builds
 # Bug 1283438
 mk_add_options AUTOCLOBBER=
 
 . "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux32/l10n-mozconfig-devedition
+++ b/browser/config/mozconfigs/linux32/l10n-mozconfig-devedition
@@ -9,17 +9,15 @@ if test `uname -m` = "x86_64"; then
   ac_add_options --host=i686-pc-linux
 fi
 
 export MOZILLA_OFFICIAL=1
 
 # Enable Telemetry
 export MOZ_TELEMETRY_REPORTING=1
 
-ac_add_options --disable-stdcxx-compat
-
 # Don't autoclobber l10n, as this can lead to missing binaries and broken builds
 # Bug 1283438
 mk_add_options AUTOCLOBBER=
 # Enable MOZ_ALLOW_LEGACY_EXTENSIONS
 ac_add_options "MOZ_ALLOW_LEGACY_EXTENSIONS=1"
 
 . "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux64/l10n-mozconfig
+++ b/browser/config/mozconfigs/linux64/l10n-mozconfig
@@ -4,15 +4,13 @@ ac_add_options --with-branding=browser/b
 
 . "$topsrcdir/build/mozconfig.no-compile"
 
 export MOZILLA_OFFICIAL=1
 
 # Enable Telemetry
 export MOZ_TELEMETRY_REPORTING=1
 
-ac_add_options --disable-stdcxx-compat
-
 # Don't autoclobber l10n, as this can lead to missing binaries and broken builds
 # Bug 1283438
 mk_add_options AUTOCLOBBER=
 
 . "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux64/l10n-mozconfig-devedition
+++ b/browser/config/mozconfigs/linux64/l10n-mozconfig-devedition
@@ -4,18 +4,16 @@ ac_add_options --with-branding=browser/b
 
 . "$topsrcdir/build/mozconfig.no-compile"
 
 export MOZILLA_OFFICIAL=1
 
 # Enable Telemetry
 export MOZ_TELEMETRY_REPORTING=1
 
-ac_add_options --disable-stdcxx-compat
-
 # Don't autoclobber l10n, as this can lead to missing binaries and broken builds
 # Bug 1283438
 mk_add_options AUTOCLOBBER=
 
 # Enable MOZ_ALLOW_LEGACY_EXTENSIONS
 ac_add_options "MOZ_ALLOW_LEGACY_EXTENSIONS=1"
 
 . "$topsrcdir/build/mozconfig.common.override"

--- a/browser/config/mozconfigs/linux64/nightly-fuzzing-asan
+++ b/browser/config/mozconfigs/linux64/nightly-fuzzing-asan
@@ -5,17 +5,17 @@ ac_add_options --enable-optimize="-O2 -g
 . $topsrcdir/build/mozconfig.stylo
 
 # ASan specific options on Linux
 ac_add_options --enable-valgrind
 
 . $topsrcdir/build/unix/mozconfig.fuzzing
 
 ac_add_options --enable-fuzzing
-ac_add_options --disable-stdcxx-compat
+unset MOZ_STDCXX_COMPAT
 
 export PKG_CONFIG_LIBDIR=/usr/lib64/pkgconfig:/usr/share/pkgconfig
 . $topsrcdir/build/unix/mozconfig.gtk
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
 
 # Need this to prevent name conflicts with the normal nightly build packages

--- a/build/moz.configure/old.configure
+++ b/build/moz.configure/old.configure
@@ -211,17 +211,16 @@ def old_configure_options(*options):
     '--enable-pulseaudio',
     '--enable-raw',
     '--enable-readline',
     '--enable-reflow-perf',
     '--enable-sandbox',
     '--enable-signmar',
     '--enable-startup-notification',
     '--enable-startupcache',
-    '--enable-stdcxx-compat',
     '--enable-strip',
     '--enable-synth-pico',
     '--enable-system-cairo',
     '--enable-system-extension-dirs',
     '--enable-system-pixman',
     '--enable-system-sqlite',
     '--enable-tasktracer',
     '--enable-thread-sanitizer',

--- a/build/moz.configure/toolchain.configure
+++ b/build/moz.configure/toolchain.configure
@@ -1543,8 +1543,36 @@ js_option('--enable-coverage', env='MOZ_
 @depends('--enable-coverage')
 def code_coverage(value):
     if value:
         return True
 
 
 set_config('MOZ_CODE_COVERAGE', code_coverage)
 set_define('MOZ_CODE_COVERAGE', code_coverage)
+
+# Libstdc++ compatibility hacks
+# ==============================================================
+#
+js_option('--enable-stdcxx-compat', env='MOZ_STDCXX_COMPAT',
+          help='Enable compatibility with older libstdc++')
+
+
+@template
+def libstdcxx_version(var, compiler):
+    @depends(compiler, when='--enable-stdcxx-compat')
+    @imports(_from='mozbuild.configure.libstdcxx', _import='find_version')
+    def version(compiler):
+        result = find_version(
+            compiler.wrapper + [compiler.compiler] + compiler.flags)
+        if result:
+            return str(result)
+
+    set_config(var, version)
+    return version
+
+
+add_gcc_flag(
+    '-D_GLIBCXX_USE_CXX11_ABI=0', cxx_compiler,
+    when=libstdcxx_version('MOZ_LIBSTDCXX_TARGET_VERSION', cxx_compiler))
+add_gcc_flag(
+    '-D_GLIBCXX_USE_CXX11_ABI=0', host_cxx_compiler,
+    when=libstdcxx_version('MOZ_LIBSTDCXX_HOST_VERSION', host_cxx_compiler))

--- a/build/mozconfig.no-compile
+++ b/build/mozconfig.no-compile
@@ -12,8 +12,10 @@ unset CXX
 unset HOST_CC
 unset HOST_CXX
 unset RUSTC
 unset CARGO
 unset MAKECAB
 unset TOOLCHAIN_PREFIX
 unset BINDGEN_CFLAGS
 unset LLVM_CONFIG
+
+unset MOZ_STDCXX_COMPAT

--- a/build/unix/mozconfig.stdcxx
+++ b/build/unix/mozconfig.stdcxx
@@ -1,10 +1,10 @@
 # Avoid dependency on libstdc++ 4.7
-ac_add_options --enable-stdcxx-compat
+export MOZ_STDCXX_COMPAT=1
 
 TOOLTOOL_DIR=${TOOLTOOL_DIR:-$topsrcdir}
 
 if [ -f "$TOOLTOOL_DIR/gcc/lib/libstdc++.so" ]; then
   # We put both 32-bits and 64-bits library path in LD_LIBRARY_PATH: ld.so
   # will prefer the files in the 32-bits path when loading 32-bits executables,
   # and the files in the 64-bits path when loading 64-bits executables.
   LD_LIBRARY_PATH=${LD_LIBRARY_PATH:+$LD_LIBRARY_PATH:}$TOOLTOOL_DIR/gcc/lib64:$TOOLTOOL_DIR/gcc/lib

--- a/old-configure.in
+++ b/old-configure.in
@@ -3776,33 +3776,16 @@ dnl ====================================
 dnl = Enable stripping of libs & executables when packaging
 dnl ========================================================
 MOZ_ARG_ENABLE_BOOL(install-strip,
 [  --enable-install-strip  Enable stripping of libs & executables when packaging ],
     PKG_SKIP_STRIP= ,
     PKG_SKIP_STRIP=1)
 
 dnl ========================================================
-dnl = libstdc++ compatibility hacks
-dnl ========================================================
-
-STDCXX_COMPAT=
-MOZ_ARG_ENABLE_BOOL(stdcxx-compat,
-[  --enable-stdcxx-compat  Enable compatibility with older libstdc++],
-    STDCXX_COMPAT=1)
-
-if test -n "$STDCXX_COMPAT" -a -n "$COMPILE_ENVIRONMENT"; then
-   eval $(CXX="$CXX" HOST_CXX="$HOST_CXX" $PYTHON -m mozbuild.configure.libstdcxx)
-   AC_SUBST(MOZ_LIBSTDCXX_TARGET_VERSION)
-   AC_SUBST(MOZ_LIBSTDCXX_HOST_VERSION)
-   CXXFLAGS="$CXXFLAGS -D_GLIBCXX_USE_CXX11_ABI=0"
-   HOST_CXXFLAGS="$HOST_CXXFLAGS -D_GLIBCXX_USE_CXX11_ABI=0"
-fi
-
-dnl ========================================================
 dnl = frontend JS debug mode
 dnl ========================================================
 
 MOZ_ARG_ENABLE_BOOL(debug-js-modules,
 [  --enable-debug-js-modules  Enable debug mode for frontend JS libraries],
    DEBUG_JS_MODULES=1,
    DEBUG_JS_MODULES=)
 

--- a/python/mozbuild/mozbuild/configure/libstdcxx.py
+++ b/python/mozbuild/mozbuild/configure/libstdcxx.py
@@ -50,32 +50,34 @@ def cmp_ver(a, b):
     return 0
 
 def encode_ver(v):
     """Encode the version as a single number.
     """
     t = split_ver(v)
     return t[0] << 16 | t[1] << 8 | t[2]
 
-def find_version(e):
-    """Given the value of environment variable CXX or HOST_CXX, find the
-    version of the libstdc++ it uses.
+def find_version(args):
+    """Given a base command line for a compiler, find the version of the
+    libstdc++ it uses.
     """
-    args = e.split()
     args +=  ['-shared', '-Wl,-t']
     p = subprocess.Popen(args, stderr=subprocess.STDOUT, stdout=subprocess.PIPE)
     candidates = [x for x in p.stdout if 'libstdc++.so' in x]
     if not candidates:
         return ''
     assert len(candidates) == 1
     libstdcxx = parse_ld_line(candidates[-1])
 
     p = subprocess.Popen(['readelf', '-V', libstdcxx], stdout=subprocess.PIPE)
     versions = [parse_readelf_line(x)
                 for x in p.stdout.readlines() if 'Name: GLIBCXX' in x]
     last_version = sorted(versions, cmp = cmp_ver)[-1]
     return encode_ver(last_version)
 
 if __name__ == '__main__':
+    """Given the value of environment variable CXX or HOST_CXX, find the
+    version of the libstdc++ it uses.
+    """
     cxx_env = os.environ['CXX']
-    print('MOZ_LIBSTDCXX_TARGET_VERSION=%s' % find_version(cxx_env))
+    print('MOZ_LIBSTDCXX_TARGET_VERSION=%s' % find_version(cxx_env.split()))
     host_cxx_env = os.environ.get('HOST_CXX', cxx_env)
-    print('MOZ_LIBSTDCXX_HOST_VERSION=%s' % find_version(host_cxx_env))
+    print('MOZ_LIBSTDCXX_HOST_VERSION=%s' % find_version(host_cxx_env.split()))