title: How to add pre-build step in qmake/qtcreator?
body: <p>I want the compiled application to have the commit number, source files checksums and other things to be available during the compilation.</p>
  
  <p>In plain Makefiles I do like this:</p>
  
  <pre><code>prog: VERSION source.c
      gcc -DVERSION=\"$(shell cat VERSION)\" source.c -o prog 
  
  VERSION: .git
      git describe &gt; VERSION
  </code></pre>
  
  <p>How to use something similar with qmake?</p>