Roll Clang from ca6196138012 to 20d06c833d83

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/clang-dart-sdk
Please CC dart-vm-gardener@grotations.appspotmail.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Clang: https://bugs.fuchsia.dev/p/fuchsia/issues/list?q=component%3AToolchain
To file a bug in Dart SDK: https://github.com/dart-lang/sdk/issues

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

Cq-Include-Trybots: luci.dart.try:dart-sdk-linux-try;luci.dart.try:dart-sdk-mac-try;luci.dart.try:dart-sdk-mac-arm64-try;luci.dart.try:dart-sdk-win-try
Change-Id: I7c28885f64bf1f16feebc751d1ef934fe89bf08d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/279600
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

DEPS

@@ -74,7 +74,7 @@ vars = {
   # The list of revisions for these tools comes from Fuchsia, here:
   # https://fuchsia.googlesource.com/integration/+/HEAD/toolchain
   # If there are problems with the toolchain, contact fuchsia-toolchain@.
-  "clang_version": "git_revision:ca619613801233ef2def8c3cc7d311d5ed0033cb",
+  "clang_version": "git_revision:20d06c833d833ef6b2d0f519cc4a7998d49a2803",
   "gn_version": "git_revision:0bcd37bd2b83f1a9ee17088037ebdfe6eab6d31a",
 
   # Update from https://chrome-infra-packages.appspot.com/p/fuchsia/sdk/gn