title: After upgrade to qt 5.5.0 I got warning for QML imports
body: <p>I just upgraded from 5.4.1 to 5.5.0 today. But when I build my android project I get these lines of warning in compile output:</p>
  
  <pre><code>Warning: QML import could not be resolved in any of the import paths: QtQuick.Extras.Private
  Warning: QML import could not be resolved in any of the import paths: QtQuick.Extras.Private.CppUtils
  Warning: QML import could not be resolved in any of the import paths: QtQuick.Extras.Private.CppUtils
  Warning: QML import could not be resolved in any of the import paths: HelperWidgets
  </code></pre>
  
  <p>What is this? My project compiles without any warnings in the previous version.</p>