title: Variable that refers to the project directory in Qt Creator?
body: <p>I'm working on a cross-platform Qt application and the paths are different on Mac OS X and Windows. Since the project is on an external hard-drive, the drive letter also occasionally changes on Windows.</p>
  
  <p>For that reason, I would like to refer to the project directory using a variable, preferably a built-in one. In particular, is there such a variable usable in:</p>
  
  <ul>
  <li>The .pro file?</li>
  <li>The build settings (in the Projects tab)?</li>
  </ul>