Add non-system-border option on Windows

Sine Striker

2023-12-22 c837319767bb609c6ec806336e49a347c77b11d3

 src/widgets/widgetwindowagent.cpp

@@ -36,9 +36,7 @@
        w->setAttribute(Qt::WA_DontCreateNativeAncestors);
        w->setAttribute(Qt::WA_NativeWindow);

        if (!d->setup(w, new WidgetItemDelegate())) {
            return false;
        }
        d->setup(w, new WidgetItemDelegate());
        d->hostWidget = w;

#ifdef Q_OS_WINDOWS