message: Use unversioned clang/clang++ if versioned binaries don't exist.
  Depending on the platform, there might not be a versioned binary
  such as clang-12 available. Fall back to simply clang then.
diff: @@ -19,6 +19,10 @@ set -e
  source ./.github/settings.sh
  if [[ "${MODE}" == *-clang ]]; then
  + # Baseline in case we don't find a specific version below
  + export CXX=clang++
  + export CC=clang
  +
  # clang versions supported. Starting with 13, we
  # get some warnings in absl, so let's not go beyond
  # 12 for now.
  