Merge topic 'cxxmodules-pch'

40dc13b242 cmNinjaTargetGenerator: PCH files do not need dyndep
f61c64cd1c cmLocalGenerator: prevent scanning of PCH source files
ea8c37b759 Tests/CXXModules: add a test which scans a PCH-using source

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !9032