title: How to build against older iOS versions with the latest Xcode downloads?
body: <p>I have multiple versions of Xcode installed. I can build my project against older iOS versions by launching old Xcode. But how could I use newer Xcode versions to build against older iOS versions?</p>
  
  <p>In the project settings there's a Base SDK dropdown. It only offers the very latest iOS version for selection.</p>
  
  <p>Under /Developer/Platforms/ there is an iOS.platform folder which contains this:</p>
  
  <pre><code>SDKs/
    iPhoneOS3.2.sdk
    iPhoneOS4.1.sdk
  </code></pre>
  
  <p>And finally, there is an interesting folder called DeviceSupport, which contains a whole bunch of versions ranging from 3.0 to 4.1!</p>
  
  <p>There must be a way to copy SDKs / DeviceSupport files from old Xcode to new Xcode and make the older ones like iOS 4.0 or even 3.0 working. How?</p>