Debugger: Fix QML extra stack loading for GDB

Change-Id: I702bb8f183e93fe25857115225fa55607ffb1674
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/debugger/qml/qmlcppengine.h

@@ -123,6 +123,7 @@ protected:
 
     void notifyInferiorSetupOk() override;
     void notifyEngineRemoteServerRunning(const QString &, int pid) override;
+    void loadAdditionalQmlStack() override;
 
 private:
     void engineStateChanged(DebuggerState newState);