Merge topic 'cxxmodules-non-compiled-source'

24a9b00f83 Merge branch 'cxxmodules-non-compiled-source-release' into cxxmodules-non-compiled-source
458e3974a8 cxxmodules: detect and message about non-compiled sources

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !8773