Run Clang plugin tests on the ToT bots

BUG=452726

Review URL: https://codereview.chromium.org/1132123003

Cr-Commit-Position: refs/heads/master@{#330379}

tools/clang/scripts/update.py

@@ -295,7 +295,7 @@ def UpdateClang(args):
       CopyFile(os.path.join(sanitizer_include_dir, f),
                aux_sanitizer_include_dir)
 
-  if args.run_tests:
+  if args.run_tests or use_head_revision:
     os.chdir(LLVM_BUILD_DIR)
     RunCommand(GetVSVersion().SetupScript('x64') +
                ['&&', 'ninja', 'cr-check-all'])

tools/clang/scripts/update.sh

@@ -698,9 +698,11 @@ if [[ -n "${with_android}" ]]; then
   popd
 fi
 
-if [[ -n "$run_tests" ]]; then
+if [[ -n "$run_tests" -o -n ${LLVM_FORCE_HEAD_REVISION:-''} ]]; then
   # Run Chrome tool tests.
   ninja -C "${LLVM_BUILD_DIR}" cr-check-all
+fi
+if [[ -n "$run_tests" ]]; then
   # Run the LLVM and Clang tests.
   ninja -C "${LLVM_BUILD_DIR}" check-all
 fi