Merge topic 'cpp-named-module-file-sets'

07bc3b07ec gitlab-ci: test C++ modules using GCC
1b2270aa4e ci: add a Docker image to test out C++ modules with GCC
8c5a53096a Tests/RunCMake/CXXModules: add module-using examples
4151547e2f cmGlobalNinjaGenerator: use `cmModuleMapper` implementation
b43bdaff3c cmCxxModuleMapper: implement support for GCC's module map format
02d0f0e752 cmCxxModuleMapper: add source to handle module mapper contents
a046a45aad cmGlobalNinjaGenerator: add a TODO for header units
386465bf83 cmTarget: add support for C++ module fileset types
...

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !7369