Merge topic 'find_dependency-dedup'

fb9a3d0c7d find_dependency: Avoid repeating identical dependency searches
5fbda0f572 find_dependency: Unset temporary variables before returning
591b75ee17 Tests: Add case covering transitive find_dependency calls

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !7936