ProjectExplorer: Use RAII pattern for parsing start/stop signalling

Change-Id: I13de537140f265db3e3d0ab1cd924d6897cd90c8
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/cmakeprojectmanager/cmakeproject.h

@@ -121,6 +121,8 @@ private:
     QTimer m_delayedParsingTimer;
     int m_delayedParsingParameters = 0;
 
+    ParseGuard m_parseGuard;
+
     friend class Internal::CMakeBuildConfiguration;
     friend class Internal::CMakeBuildSettingsWidget;
 };