Merge topic 'misc-cxx-modules-fixes'

28ece63fee cxxmodules: Fix exported path to installed module sources in subdirs
f2a699261b cxxmodules: Do not expect collator install scripts with no CXX_MODULES
f9677cc122 Tests: Improve RunCMake.CXXModules expectation matching and error reporting

Acked-by: Kitware Robot <kwrobot@kitware.com>
Reviewed-by: Ben Boeckel <ben.boeckel@kitware.com>
Merge-request: !8474