Revert "Roll clang llvmorg-12-init-5035-gd0abc757-2 : llvmorg-12-init-5627-gf086e85e-1."

But keep the rpmalloc change, so this builds a new -3 package with the
old LLVM rev instead of just pointing us at the old d0abc757-2 (which
doesn't have rpmalloc).

The roll seems to cause problems in builds that use thinlto
(https://crbug.com/1128966, https://crbug.com/1128144).

Bug: 1128966,1128144,1126953
Change-Id: I1942eceb86f75d12ec1916cf7831fee221b01f8e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2422159
Commit-Queue: Nico Weber <thakis@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809133}

build/config/compiler/BUILD.gn

@@ -503,8 +503,8 @@ config("compiler") {
 
     # Pinned clang has enable-dse-memoryssa enabled by default but it's broken,
     # so we have to force it off.
-    # Trunk clang has it disabled by default but it might work, so we force it on
-    # so the ToT bots can check if it works now.
+    # Trunk clang has it disabled by default but it might work, so we force it
+    # on so the ToT bots can check if it works now.
     if (!llvm_force_head_revision) {
       cflags += [
         # TODO(https://crbug.com/1127713): Investigate, remove.

tools/clang/scripts/update.py

@@ -38,8 +38,8 @@ import zipfile
 # https://chromium.googlesource.com/chromium/src/+/master/docs/updating_clang.md
 # Reverting problematic clang rolls is safe, though.
 # This is the output of `git describe` and is usable as a commit-ish.
-CLANG_REVISION = 'llvmorg-12-init-5627-gf086e85e'
-CLANG_SUB_REVISION = 2
+CLANG_REVISION = 'llvmorg-12-init-5035-gd0abc757'
+CLANG_SUB_REVISION = 3
 
 PACKAGE_VERSION = '%s-%s' % (CLANG_REVISION, CLANG_SUB_REVISION)
 RELEASE_VERSION = '12.0.0'