message: Make clang tidy 'seen' cache dependent on changes in configuration.
  Whenever the clang-tidy configuration changes, make sure that we
  re-process all files by including the configuration into the
  content hash creation.
diff: @@ -50,11 +50,12 @@ cat bazel-bin/compile_commands.json \
  # (TODO: could the tidy result be different if an include content changes ?
  # Then we have to do g++ -E (using compilation database knowing about -I etc.)
  # or combine hashes of all mentioned #includes that are also in our list)
  -find . -name "*.cc" -and -not -name "*test*.cc" \
  +# Make need to re-run file dependent on clang-tidy configuration + file content.
  +for f in $(find . -name "*.cc" -and -not -name "*test*.cc" \
  -or -name "*.h" -and -not -name "*test*.h" \
  - | grep -v "verilog/tools/kythe" \
  - | xargs md5sum | sort \
  - > ${CLANG_TIDY_SEEN_CACHE}.new
  + | grep -v "verilog/tools/kythe") ; do
  + (echo $CLANG_TIDY ; cat .clang-tidy $f) | md5sum | sed "s|-|$f|g"
  +done | sort > ${CLANG_TIDY_SEEN_CACHE}.new
  join -v2 ${CLANG_TIDY_SEEN_CACHE} ${CLANG_TIDY_SEEN_CACHE}.new \
  | awk '{print $2}' | sort > ${FILES_TO_PROCESS}
  