[ChangeLog][CMake] The target-based variant of qt6_add_resource gained
the option BIG_RESOURCES. This can be used instead of
qt6_add_big_resources, which is not target-based.
Fixes: QTBUG-100268
Change-Id: Ib3fa783cbfbfd10f59c2f952bc88508a91f25e26
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>