With 6.5 we try to use the native message dialog if we can, but we
didn't account for the style sheet. This restores pre-6.5 behavior for
QMessageBox.
Other dialogs will continue to be native, even if a style sheet is in
use. While this is inconsistent, the other dialogs are substantially
more functional, so switching to the Qt version because of a style sheet
being active would be a significant change of behavior.
Pick-to: 6.7 6.6 6.5
Fixes: QTBUG-120054
Change-Id: I07eae609bc360140e096c5eb7ad004ffa4422123
Reviewed-by: Oliver Eftevaag <oliver.eftevaag@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
1b71e2d894