CMake: Promote all targets to global within a scope when possible

CMake 3.21 introduced a new IMPORTED_TARGETS directory property which
we can use to promote all imported targets within a scope to be
global.

This would cover transitive non-Qt imported targets which the Qt build
system does not know about and is thus a more complete solution
compared to promoting only Qt targets.

Run a finalizer at the end of the directory scope where
find_package(Qt6) is called to promote all imported targets within
that scope to global (when requested).

The old promotion method is disabled when the CMake version is new
enough.

Pick-to: 6.2
Task-number: QTBUG-92878
Task-number: QTBUG-94528
Change-Id: I533a3bd4186eba652f878ddd72c76118c2fd8bae
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

0 files changed, 0 insertions, 0 deletions