Bug 1719812 - Upgrade llvm toolchain to 12.0.1. r=firefox-build-system-reviewers,mhentges

Differential Revision: https://phabricator.services.mozilla.com/D119493

taskcluster/ci/fetch/toolchains.yml

@@ -445,11 +445,11 @@ clang-11:
         revision: 43ff75f2c3feef64f9d73328230d34dac8832a91
 
 clang-12:
-    description: clang 12.0.0 source code
+    description: clang 12.0.1 source code
     fetch:
         type: git
         repo: https://github.com/llvm/llvm-project
-        revision: d28af7c654d8db0b68c175db5ce212d74fb5e9bc
+        revision: fed41342a82f5a3a9201819a82bf7a48313e296b
 
 clang-trunk:
     description: clang main branch source code

tools/clang-tidy/config.yaml

@@ -19,7 +19,7 @@ platforms:
 # Minimum clang-tidy version that is required for all the following checkers
 # to work properly.
 # This is also used by 'mach clang-format'
-package_version: "12.0.0"
+package_version: "12.0.1"
 clang_checkers:
   - name: -*
     publish: !!bool no