deleted file mode 100644
--- a/build/build-clang/clang-6-pre-linux64.json
+++ /dev/null
@@ -1,20 +0,0 @@
-{
-    "llvm_revision": "317840",
-    "stages": "3",
-    "build_libcxx": true,
-    "build_type": "Release",
-    "assertions": false,
-    "llvm_repo": "https://llvm.org/svn/llvm-project/llvm/trunk",
-    "clang_repo": "https://llvm.org/svn/llvm-project/cfe/trunk",
-    "compiler_repo": "https://llvm.org/svn/llvm-project/compiler-rt/trunk",
-    "libcxx_repo": "https://llvm.org/svn/llvm-project/libcxx/trunk",
-    "libcxxabi_repo": "https://llvm.org/svn/llvm-project/libcxxabi/trunk",
-    "python_path": "/usr/bin/python2.7",
-    "gcc_dir": "/builds/worker/workspace/build/src/gcc",
-    "cc": "/builds/worker/workspace/build/src/gcc/bin/gcc",
-    "cxx": "/builds/worker/workspace/build/src/gcc/bin/g++",
-    "as": "/builds/worker/workspace/build/src/gcc/bin/gcc",
-    "patches": [
-      "find_symbolizer_linux.patch"
-    ]
-}

deleted file mode 100644
--- a/build/build-clang/find_symbolizer_linux.patch
+++ /dev/null
@@ -1,58 +0,0 @@
-We currently need this patch because ASan only searches PATH to find the
-llvm-symbolizer binary to symbolize ASan traces. On testing machines, this
-can be installed in PATH easily. However, for e.g. the ASan Nightly Project,
-where we ship an ASan build, including llvm-symbolizer, to the user, we
-cannot expect llvm-symbolizer to be on PATH. Instead, we should try to look
-it up next to the binary. This patch implements the functionality for Linux
-only until there is similar functionality provided upstream.
-
-diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_file.cc b/compiler-rt/lib/sanitizer_common/sanitizer_file.cc
-index cde54bf..8daade1 100644
---- a/compiler-rt/lib/sanitizer_common/sanitizer_file.cc
-+++ b/compiler-rt/lib/sanitizer_common/sanitizer_file.cc
-@@ -21,6 +21,10 @@
- #include "sanitizer_common.h"
- #include "sanitizer_file.h"
- 
-+#if SANITIZER_LINUX
-+#include "sanitizer_posix.h"
-+#endif
-+
- namespace __sanitizer {
- 
- void CatastrophicErrorWrite(const char *buffer, uptr length) {
-@@ -156,6 +160,34 @@ char *FindPathToBinary(const char *name) {
-     if (*end == '\0') break;
-     beg = end + 1;
-   }
-+
-+#if SANITIZER_LINUX
-+  // If we cannot find the requested binary in PATH, we should try to locate
-+  // it next to the binary, in case it is shipped with the build itself
-+  // (e.g. llvm-symbolizer shipped with sanitizer build to symbolize on client.
-+  if (internal_readlink("/proc/self/exe", buffer.data(), kMaxPathLength) < 0)
-+    return nullptr;
-+
-+  uptr buf_len = internal_strlen(buffer.data());
-+
-+  /* Avoid using dirname() here */
-+  while (buf_len > 0) {
-+    if (buffer[buf_len - 1] == '/')
-+      break;
-+    buf_len--;
-+  }
-+
-+  if (!buf_len)
-+    return nullptr;
-+
-+  if (buf_len + name_len + 1 <= kMaxPathLength) {
-+    internal_memcpy(&buffer[buf_len], name, name_len);
-+    buffer[buf_len + name_len] = '\0';
-+    if (FileExists(buffer.data()))
-+      return internal_strdup(buffer.data());
-+  }
-+#endif
-+
-   return nullptr;
- }
- 

--- a/taskcluster/ci/build/linux.yml
+++ b/taskcluster/ci/build/linux.yml
@@ -474,17 +474,17 @@ linux64-asan/opt:
             - builds/releng_base_linux_64_builds.py
             - balrog/production.py
         script: "mozharness/scripts/fx_desktop_build.py"
         secrets: true
         custom-build-variant-cfg: asan-tc
         tooltool-downloads: public
         need-xvfb: true
     toolchains:
-        - linux64-clang-6-pre
+        - linux64-clang
         - linux64-gcc
         - linux64-rust
         - linux64-sccache
 
 
 linux64-asan-fuzzing/opt:
     description: "Linux64 Fuzzing Opt ASAN"
     index:
@@ -507,17 +507,17 @@ linux64-asan-fuzzing/opt:
             - builds/releng_base_linux_64_builds.py
             - balrog/production.py
         script: "mozharness/scripts/fx_desktop_build.py"
         secrets: true
         custom-build-variant-cfg: fuzzing-asan-tc
         tooltool-downloads: public
         need-xvfb: true
     toolchains:
-        - linux64-clang-6-pre
+        - linux64-clang-4
         - linux64-gcc
         - linux64-rust
         - linux64-sccache
 
 linux64-asan-reporter/opt:
     description: "Linux64 Opt ASAN Reporter Nightly"
     index:
         product: firefox
@@ -539,17 +539,17 @@ linux64-asan-reporter/opt:
             - builds/releng_base_linux_64_builds.py
             - balrog/production.py
         script: "mozharness/scripts/fx_desktop_build.py"
         secrets: true
         custom-build-variant-cfg: asan-reporter-tc
         tooltool-downloads: public
         need-xvfb: true
     toolchains:
-        - linux64-clang-6-pre
+        - linux64-clang-4
         - linux64-gcc
         - linux64-rust
         - linux64-sccache
 
 linux64-asan/debug:
     description: "Linux64 Debug ASAN"
     index:
         product: firefox
@@ -571,17 +571,17 @@ linux64-asan/debug:
             - builds/releng_base_linux_64_builds.py
             - balrog/production.py
         script: "mozharness/scripts/fx_desktop_build.py"
         secrets: true
         custom-build-variant-cfg: asan-tc-and-debug
         tooltool-downloads: public
         need-xvfb: true
     toolchains:
-        - linux64-clang-6-pre
+        - linux64-clang
         - linux64-gcc
         - linux64-rust
         - linux64-sccache
 
 linux64-nightly/opt:
     description: "Linux64 Nightly"
     attributes:
         nightly: true

--- a/taskcluster/ci/toolchain/linux.yml
+++ b/taskcluster/ci/toolchain/linux.yml
@@ -64,38 +64,16 @@ linux64-clang-5:
         resources:
             - 'build/build-clang/build-clang.py'
             - 'build/build-clang/clang-5-linux64.json'
             - 'taskcluster/scripts/misc/tooltool-download.sh'
         toolchain-artifact: public/build/clang.tar.xz
     toolchains:
         - linux64-gcc-4.9
 
-linux64-clang-6-pre:
-    description: "Clang 6 Pre toolchain build"
-    treeherder:
-        kind: build
-        platform: toolchains/opt
-        symbol: TL(clang6p)
-        tier: 1
-    worker-type: aws-provisioner-v1/gecko-{level}-b-linux
-    worker:
-        docker-image: {in-tree: desktop-build}
-        max-run-time: 7200
-    run:
-        using: toolchain-script
-        script: build-clang-6-pre-linux.sh
-        resources:
-            - 'build/build-clang/build-clang.py'
-            - 'build/build-clang/clang-6-pre-linux64.json'
-            - 'taskcluster/scripts/misc/tooltool-download.sh'
-        toolchain-artifact: public/build/clang.tar.xz
-    toolchains:
-        - linux64-gcc-4.9
-
 linux64-clang-tidy:
     description: "Clang-tidy build"
     index:
         product: static-analysis
         job-name: linux64-clang-tidy
     treeherder:
         kind: build
         platform: toolchains/opt

deleted file mode 100755
--- a/taskcluster/scripts/misc/build-clang-6-pre-linux.sh
+++ /dev/null
@@ -1,25 +0,0 @@
-#!/bin/bash
-set -x -e -v
-
-# This script is for building clang for Linux.
-
-WORKSPACE=$HOME/workspace
-HOME_DIR=$WORKSPACE/build
-UPLOAD_DIR=$HOME/artifacts
-
-cd $HOME_DIR/src
-
-. taskcluster/scripts/misc/tooltool-download.sh
-
-# 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-6-pre-linux64.json
-
-set -x
-
-# Put a tarball in the artifacts dir
-mkdir -p $UPLOAD_DIR
-cp clang.tar.* $UPLOAD_DIR