title: aboutToQuit signal not called in Android environment?
body: <p>How can i catch QApplication::aboutToQuit on Android environment ? 
  It works perfectly on Windows but it's never called when user close the application on Android. </p>
  
  <p>I'm using Qt 5.12.2, QQuick2.</p>
  
  <p>It does not work on Android Emulator and neither on my Android phone.</p>
  
  <pre><code>int main(int argc, char *argv[])
  {
      QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
  
      QGuiApplication app(argc, argv);    
      QuitEventHandle test;
      QObject::connect(&amp;app, &amp;QCoreApplication::aboutToQuit, &amp;test, &amp;QuitEventHandle::aboutToQuit);
  
      QQmlApplicationEngine engine;
      engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
      if (engine.rootObjects().isEmpty())
          return -1;        
  
      return app.exec();
  }
  
  class QuitEventHandle : public QObject
  {
      Q_OBJECT
  
  public:
      QuitEventHandle(QObject *parent=nullptr);
      virtual ~QuitEventHandle() override;
  
  public slots:
      void aboutToQuit();
  };
  
  QuitEventHandle::QuitEventHandle(QObject *parent) : QObject(parent)
  {
  }
  QuitEventHandle::~QuitEventHandle()
  {
  }
  
  void QuitEventHandle::aboutToQuit()
  {
      int a = 2;
  }
  </code></pre>