title: Qt project file and system environment variable
body: <p>I work on <code>Mac Os X</code> with <code>Qt Creator</code> and I want to use a <code>system environment variable</code> as a path in my <code>.pro</code> file. The variable is set in the <code>Project =&gt; Build Environment</code> and here's a part of my <code>pro</code> file :</p>
  
  <pre><code>DEPENDPATH += . \
          $$VLC_QT_PATH
  INCLUDEPATH += . \
          $$VLC_QT_PATH
  </code></pre>
  
  <p>and some output from the terminal :</p>
  
  <pre><code>Mac:~ me$ echo $VLC_QT_PATH
  /Users/me/vlc/include
  Mac:~ me$ cd $VLC_QT_PATH
  Mac:~ me$ find . -iname "vlc.h"
  ./vlc/vlc.h
  </code></pre>
  
  <p>But the include <code>#include "vlc/vlc.h"</code> isn't working</p>