Merge topic 'fix-cmp0199' into release-4.2

35d5a4fd6d GenEx: Partially restore pre-CMP0199 behavior of $<CONFIG>

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Acked-by: Matthew Woehlke <matthew.woehlke@kitware.com>
Merge-request: !11581