QtSupport: Don't rely on QObject parents on late destruction

Change-Id: Ibdb91c80d4932a5f0dced9843dfd01641577a88d
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/qtsupport/qtsupportplugin.cpp

@@ -135,6 +135,12 @@ void QtSupportPlugin::initialize()
     QtVersionManager::initialized();
 }
 
+ExtensionSystem::IPlugin::ShutdownFlag QtSupportPlugin::aboutToShutdown()
+{
+    QtVersionManager::shutdown();
+    return SynchronousShutdown;
+}
+
 const char kLinkWithQtInstallationSetting[] = "LinkWithQtInstallation";
 
 static void askAboutQtInstallation()

src/plugins/qtsupport/qtsupportplugin.h

@@ -19,6 +19,7 @@ public:
 private:
     void initialize() final;
     void extensionsInitialized() final;
+    ShutdownFlag aboutToShutdown() final;
 
     class QtSupportPluginPrivate *d = nullptr;
 

src/plugins/qtsupport/qtversionmanager.cpp

@@ -92,9 +92,12 @@ public:
                 this, &QtVersionManagerImpl::triggerQtVersionRestore);
     }
 
-    ~QtVersionManagerImpl()
+    void shutdown()
     {
         delete m_writer;
+        m_writer = nullptr;
+        delete m_configFileWatcher;
+        m_configFileWatcher = nullptr;
         qDeleteAll(m_versions);
         m_versions.clear();
     }
@@ -174,6 +177,11 @@ void QtVersionManager::initialized()
     qtVersionManagerImpl();
 }
 
+void QtVersionManager::shutdown()
+{
+    qtVersionManagerImpl().shutdown();
+}
+
 bool QtVersionManagerImpl::restoreQtVersions()
 {
     QTC_ASSERT(!m_writer, return false);

src/plugins/qtsupport/qtversionmanager.h

@@ -45,6 +45,8 @@ public:
                                    const QString &manifestPath,
                                    const QString &examplesPath);
 
+    static void shutdown();
+
 signals:
     // content of QtVersion objects with qmake path might have changed
     void qtVersionsChanged(const QList<int> &addedIds, const QList<int> &removedIds, const QList<int> &changedIds);