Merge topic 'find-openmp-from-system-paths'

09b4e870a5 FindOpenMP: Restore searching system paths

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Acked-by: Felix Yan <felixonmars@archlinux.org>
Merge-request: !7526