On macOS, we see unexplained white flashes of the UI when
overriding the scheme in the widget's constructor. This only
happens when running the bundle, but not when running the
executable.
Work around that problem by setting the scheme immediately
after constructing QApplication.
Pick-to: 6.8
Task-number: QTBUG-126248
Change-Id: I4a5fe467d628fca5e52e1e36f43af8143239c7fa
Reviewed-by: Doris Verria <doris.verria@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
88322f69a2