title: XCode 4.6.2 issue after update. (error: PCH file built from a different branch )
body: <p>My project works fine in previous versions of Xcode. Now I've updated to Xcode 4.6.2, and I'm getting this error:</p>
  
  <blockquote>
    <p>PCH file built from a different branch ((clang-425.0.27)) than the compiler ((clang-425.0.28))</p>
  </blockquote>
  
  <p>Is this a bug in Xcode? How do I fix it?</p>