title: Multiple configurations in Qt
body: <p>I'm new to Qt Creator and I have several questions regarding multiple build configurations.
  A side note: I have the QtCreator 1.3.1 installed on my Linux machine.</p>
  
  <p>I need to have two configurations in my Qt Creator project. The thing is that these aren't simply debug and release but are based on the target architecture - x86 or x64. I came across
      <a href="https://stackoverflow.com/questions/2259192/building-multiple-targets-in-qt-qmake">Building multiple targets in Qt / Qmake</a>
    and from that I went trying something like:</p>
  
  <pre><code>Conf_x86 {
   TARGET = MyApp_x86
  }
  
  Conf_x64 {
   TARGET = MyApp_x64
  }
  </code></pre>
  
  <p>This way however I don't seems to be able to use the Qt Creator IDE to build each of these separately (Build All, Rebuild All, etc. options from the IDE menu). Is there a way to achieve this - may be even show Conf_x86 and Conf_x64 as new build configurations in Qt Creator?</p>
  
  <p>One other thing the Qt I have is 64 bit so by default the target built using Qt Creator IDE will also be 64 bit. I noticed that the effective qmake call in the build step includes the following option <code>-spec linux-g++-64</code>. I also noticed that should I add <code>-spec linux-g++-32</code> in 'Additional arguments' it would override <code>-spec linux-g++-64</code> and the resulting target will be 32 bit.<br>
  How can I achieve this by simply editing the contents of the .pro file? I saw that all these changes are initially saved in the .pro.user file but this doesn't suit me at all. I need to be able to make these configurations from the .pro file if possible.</p>