deleted file mode 100644
--- a/build/build-clang/clang-macosx64.json
+++ /dev/null
@@ -1,29 +0,0 @@
-{
-    "llvm_revision": "289595",
-    "stages": "1",
-    "build_libcxx": true,
-    "build_type": "Release",
-    "assertions": false,
-    "osx_cross_compile": true,
-    "llvm_repo": "https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_391/final",
-    "clang_repo": "https://llvm.org/svn/llvm-project/cfe/tags/RELEASE_391/final",
-    "compiler_repo": "https://llvm.org/svn/llvm-project/compiler-rt/tags/RELEASE_391/final",
-    "libcxx_repo": "https://llvm.org/svn/llvm-project/libcxx/tags/RELEASE_391/final",
-    "libcxxabi_repo": "https://llvm.org/svn/llvm-project/libcxxabi/tags/RELEASE_391/final",
-    "python_path": "/usr/bin/python2.7",
-    "gcc_dir": "/builds/worker/workspace/build/src/gcc",
-    "cc": "/builds/worker/workspace/build/src/clang/bin/clang",
-    "cxx": "/builds/worker/workspace/build/src/clang/bin/clang++",
-    "as": "/builds/worker/workspace/build/src/clang/bin/clang",
-    "ar": "/builds/worker/workspace/build/src/cctools/bin/x86_64-apple-darwin11-ar",
-    "ranlib": "/builds/worker/workspace/build/src/cctools/bin/x86_64-apple-darwin11-ranlib",
-    "libtool": "/builds/worker/workspace/build/src/cctools/bin/x86_64-apple-darwin11-libtool",
-    "ld": "/builds/worker/workspace/build/src/clang/bin/clang",
-    "patches":[
-      "llvm-debug-frame.patch",
-      "compiler-rt-cross-compile.patch",
-      "pr28831-r280042.patch",
-      "r277806.patch",
-      "r285657.patch"
-    ]
-}

deleted file mode 100644
--- a/build/build-clang/pr28831-r280042.patch
+++ /dev/null
@@ -1,19 +0,0 @@
-Backport the fix to PR28831 plus its follow-up (r280042)
-
-diff --git a/libcxx/lib/CMakeLists.txt b/libcxx/lib/CMakeLists.txt
-index afc388e76..4f43f3711 100644
---- a/libcxx/lib/CMakeLists.txt
-+++ b/libcxx/lib/CMakeLists.txt
-@@ -115,9 +115,9 @@ if ( APPLE AND (LIBCXX_CXX_ABI_LIBNAME STREQUAL "libcxxabi" OR
-       "-Wl,-unexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/libc++unexp.exp"
-       "/usr/lib/libSystem.B.dylib")
-   else()
--    if ( ${CMAKE_OSX_SYSROOT} )
--      list(FIND ${CMAKE_OSX_ARCHITECTURES} "armv7" OSX_HAS_ARMV7)
--      if (OSX_HAS_ARMV7)
-+    if (DEFINED CMAKE_OSX_SYSROOT)
-+      list(FIND CMAKE_OSX_ARCHITECTURES "armv7" OSX_HAS_ARMV7)
-+      if (NOT OSX_HAS_ARMV7 EQUAL -1)
-         set(OSX_RE_EXPORT_LINE
-           "${CMAKE_OSX_SYSROOT}/usr/lib/libc++abi.dylib"
-           "-Wl,-reexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/libc++sjlj-abi.exp")

--- a/taskcluster/ci/toolchain/macosx.yml
+++ b/taskcluster/ci/toolchain/macosx.yml
@@ -22,17 +22,17 @@ macosx64-clang:
         env:
             TOOLTOOL_MANIFEST: "browser/config/tooltool-manifests/macosx64/cross-clang.manifest"
     run:
         using: toolchain-script
         script: build-clang-macosx.sh
         tooltool-downloads: internal
         resources:
             - 'build/build-clang/build-clang.py'
-            - 'build/build-clang/clang-macosx64.json'
+            - 'build/build-clang/clang-6-macosx64.json'
             - 'taskcluster/scripts/misc/tooltool-download.sh'
         toolchain-artifact: public/build/clang.tar.xz
     toolchains:
         - linux64-cctools-port
         - linux64-clang-6
         - linux64-gcc-4.9
 
 macosx64-clang-tidy:

--- a/taskcluster/scripts/misc/build-clang-macosx.sh
+++ b/taskcluster/scripts/misc/build-clang-macosx.sh
@@ -19,15 +19,15 @@ export CROSS_SYSROOT=$HOME_DIR/src/MacOS
 export PATH=$PATH:$CROSS_CCTOOLS_PATH/bin
 ln -sf $CROSS_CCTOOLS_PATH/bin/x86_64-apple-darwin11-lipo $CROSS_CCTOOLS_PATH/bin/lipo
 
 # gets a bit too verbose here
 set +x
 
 cd build/build-clang
 # |mach python| sets up a virtualenv for us!
-../../mach python ./build-clang.py -c clang-macosx64.json
+../../mach python ./build-clang.py -c clang-6-macosx64.json
 
 set -x
 
 # Put a tarball in the artifacts dir
 mkdir -p $UPLOAD_DIR
 cp clang.tar.* $UPLOAD_DIR