The test shows an application modal QMessageBox, but assumes that doing
so will be non-blocking, which for macOS is not the case (yet). Instead
of making the dialog window-modal, which would potentially affect the
logic of the test, we disable native dialogs. This should be fine, as
the purpose of the test is to test the is_closing logic of
closeAllWindows, which lives on a layer above the native dialogs.
Pick-to: 6.5
Change-Id: I6d627984a6ca452b876f34404b669fce41a00851
Reviewed-by: Doris Verria <doris.verria@qt.io>
ad31b5f4c7