QGstTools: Fix warning about unused m_intervalTimer

Clang does complain about this member not being used.

Change-Id: I02919715be43486f4646ca75deea66fc8a6a2276
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/gsttools/qgstreamerbushelper.cpp

@@ -118,7 +118,9 @@ private:
     guint m_tag;
     GstBus* m_bus;
     QGstreamerBusHelper*  m_helper;
+#ifdef QT_NO_GLIB
     QTimer*     m_intervalTimer;
+#endif
 
 private slots:
     void doProcessMessage(const QGstreamerMessage& msg)