Fix bogus setAttribute setter warning

Since e9e16c7464 running webengine application you can get
warning "Attribute Qt::AA_ShareOpenGLContexts must be set before
QCoreApplication is created."

WebEngine set shared open gl context on qt_call_pre_routines, so
when QCoreApplicationPrivate init() runs.

Fixes: QTBUG-76391
Change-Id: I5fc146ed70054b0c1597fe06615cea2d7a8969d8
Reviewed-by: Kai Koehne <kai.koehne@qt.io>

src/corelib/kernel/qcoreapplication.cpp

@@ -979,7 +979,11 @@ void QCoreApplication::setAttribute(Qt::ApplicationAttribute attribute, bool on)
         QCoreApplicationPrivate::attribs |= 1 << attribute;
     else
         QCoreApplicationPrivate::attribs &= ~(1 << attribute);
+#if defined(QT_NO_QOBJECT)
     if (Q_UNLIKELY(qApp)) {
+#else
+    if (Q_UNLIKELY(QCoreApplicationPrivate::is_app_running)) {
+#endif
         switch (attribute) {
             case Qt::AA_EnableHighDpiScaling:
             case Qt::AA_DisableHighDpiScaling: