Merge topic 'cxx-module-extensions'

45d1925efc Treat '.ccm', '.cxxm', and '.c++m' files as C++ sources
8c96d145c1 Tests/RunCMake: Match 'Tried extensions' output more robustly

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Acked-by: Ben Boeckel <ben.boeckel@kitware.com>
Merge-request: !8308