Merge topic 'deprecate-pre-3.10'

4c4f173876 Clarify advice given by compatibility deprecation message for CMake < 3.10

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Acked-by: Dženan Zukić <dzenan.zukic@kitware.com>
Merge-request: !9996