AutoTest: Avoid triggering run tests while building

Disable respective actions while a build is running to avoid strange
side-effects or race conditions.

Change-Id: Ifc8d1c9fc9fd4d705cabd148b145708e23029dba
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/autotest/autotestplugin.h

@@ -60,7 +60,7 @@ private:
     void updateMenuItemsEnabledState();
     QList<QObject *> createTestObjects() const override;
     const QSharedPointer<TestSettings> m_settings;
-    TestFrameworkManager *m_frameworkManager = 0;
+    TestFrameworkManager *m_frameworkManager = nullptr;
 };
 
 } // namespace Internal