title: QT: Build old project with old clang compiler on Mac with up-to-date QT version and Clang
body: <p>Motivation:  As part of my daily work, I need from time to time, to solve issues on old version of my application.
  Issue: I have a bug which I need to fix on old version. This version was built and compiled with QT 4.7.4 ( QT Creator 2.4.1).
  I have QT 5.2 on my Mac machine (Os version: 10.9.3, Clang: 5.1 LLVM 3.4svn) so I installed QtSDK (4.7.4) as well.</p>
  
  <p>No matter what I tried to do, I could find a way to install old version of Clang compiler and configure QTCreator to use it. 
  I know I need CLang 4.1 LLVM 3.1svn but QTCreator 2.4.1 (for Qt 4.7.4) cannot find it or use it .</p>
  
  <p>The bottom line: How can I have several versions of Clang compiler on my Mac and how can I set QTCreator to use specific compiler?
  I would expect it to be simple just as I have Visual Studio 2005, 2010 and 2012 on my one Windows platform and each of which uses it's own relevant compiler. </p>
  
  <p>Thanks</p>