"mac" scope in qmake actually means all mac platforms,
just like "darwin", aka macOS, iOS, watchOS, etc.
Regenerate corelib, gui and testlib after this modification.
This is a requirement for the iOS port.
Change-Id: I029c7e907d13f6ec31816a08602a5930f9ac16a7
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: Qt CMake Build Bot