Merge topic 'clang-libstdcpp-support'

5750fcd7b4 ci: enable `import_std23` module compilation with clang
52e2785018 experimental/CXXModules: recycle the UUID
28333c4516 Clang/CXXImportStd: support `-stdlib=libstdc++`

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !10727