title: Issue setting QMAKESPEC environment variable
body: <p>Refer to this post compile a Xcode project in command line
  <a href="https://stackoverflow.com/questions/377992/building-xcode-projects-from-the-command-line">Building Qt Xcode Projects From the Command Line</a>
  the QMAKESPEC variable was unable to set to macx-g++. </p>
  
  <p>I was doing like this in terminal <code>QMAKESPEC=macx-g++</code> but this still not able to generate a make file of my Xcode project for me.</p>
  
  <p>What is the right way to setup the QMAKESPEC environment variable?</p>