Merge topic 'cxxmodules-depend-on-modmap-file'

363300ac cxxmodules: depend on the modmap contents
940628d4 Tests/CXXModules: test that objects depend on their modmap files
681ee920 Tests/CXXModules: support testing rebuild conditions

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !9248