Merge topic 'set_environment_generator'

3c3bce133d cmake: Honor CMAKE_GENERATOR env var in --help output

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Acked-by: Alex Turbov <i.zaufi@gmail.com>
Merge-request: !7808