Update by review

tools/distrib/clang_tidy_code.sh

@@ -25,7 +25,7 @@ REPO_ROOT=$(pwd)
 # let's get a list of them using query command and pass it to gen_compilation_database.py
 export MANUAL_TARGETS=$(bazel query 'attr("tags", "manual", tests(//test/cpp/...))' | grep -v _on_ios)
 
-# generate a clang compilation database
+# generate a clang compilation database for all C/C++ sources in the repo.
 tools/distrib/gen_compilation_database.py \
   --include_headers \
   --ignore_system_headers \

tools/run_tests/sanity/sanity_tests.yaml

@@ -24,8 +24,8 @@
 - script: tools/distrib/check_pytype.sh
 - script: tools/distrib/clang_format_code.sh
 - script: tools/distrib/clang_tidy_code.sh
-  # ClangTidy needs to run exclusively because it runs bazel making changes
-  # and it needs many CPUs to parse all source files to be diagnosed.
+  # ClangTidy needs to run exclusively because it uses files under the bazel output
+  # directory and this will be removed by another bazel invocation.
   cpu_cost: 1000
 - script: tools/distrib/pylint_code.sh
 - script: tools/distrib/python/check_grpcio_tools.py