message: Use latest available compier for c++2x CI tests.
  Assuming that these will be the most accurate about
  complaining about problems.
diff: @@ -162,11 +162,11 @@ jobs:
  apt -qqy update
  apt -qq -y install build-essential wget git python3 python-is-python3 default-jdk cmake python3-pip
  apt -qq -y install gcc-10 g++-10
  - apt -qq -y install gcc-11 g++-11
  + apt -qq -y install gcc-12 g++-12
  apt -qq -y install clang-12 # clang always a particular version.
  source ./.github/settings.sh
  - # Use newer compiler for c++23 compilation
  - ./.github/bin/set-compiler.sh $([ "$MODE" == "test-c++23" ] && echo 11 || echo 10)
  + # Use newer compiler for c++2x compilation
  + ./.github/bin/set-compiler.sh $([[ "$MODE" == test-c++2* ]] && echo 12 || echo 10)
  ./.github/bin/install-bazel.sh
  - name: Build Slang
  