Merge topic 'cxxmodules-no-export-basedirs-as-include-paths' into release-3.29

65bd837786 Merge branch 'backport-3.28-cxxmodules-no-export-basedirs-as-include-paths'
028f3134e5 cmExportFileGenerator: only export include paths for HEADERS file sets

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !9295