title: Unknown module(s) in QT: core gui widgets
body: <p>I just installed Qt5.4.1 MSVC2013 on windows, and when I tried to build a project, I encountered an error like </p>
  
  <pre><code>Unknown module(s) in QT: core gui widgets.
  </code></pre>
  
  <p>Then I add a user environment variable path</p>
  
  <pre><code>D:\Program Files\Qt\5.4\msvc2013_64;
  </code></pre>
  
  <p>but the problem still exests.</p>
  
  <p>I search the internet but it seems no one ever gets similar problem... it really confuses me.</p>