Merge topic 'enable_warnings'

373b29bd3f Rename {_ => }CMAKE_INCLUDE_SYSTEM_FLAG_${lang}_WARNING

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Reviewed-by: Ben Boeckel <ben.boeckel@kitware.com>
Acked-by: Marcel Raad <marcel.raad@teamviewer.com>
Merge-request: !9688