To support per-target iOS launch screens we need a way to specify
custom Info.plist entries without using cache variables, which we were
forced to use due to the implicit configure_file done for
MACOSX_BUNDLE_INFO_PLIST.
We now introduce an extra configure_file call done in a finalizer,
before we hand off the Info.plist file to MACOSX_BUNDLE_INFO_PLIST.
This extra configure_file call allows us to insert / substitute
additional Info.plist entries that CMake does not allow setting.
If a custom Info.plist file is provided, the finalizer will simply
skip the logic for creating a new one.
Amends e5b3436255ce095af58608b03b913fc9bcb8e61f
Pick-to: 6.4
Fixes: QTBUG-101064
Change-Id: I65496da146c9430a949a8163817021d54da28386
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
578f4ba00c