title: incompatible SDK for ARC with mac osx 10.10
body: <p>I am getting annoying warning messages for my targets after upgrading to osx 10.10, and the latest xcode (I can't remember which actually triggered it)</p>
  
  <p>e.g: Incompatible SDK for ARC in target ApplicationName: macosx</p>
  
  <p>If I change it from 'latest' to '10.10' then I get the same error:</p>
  
  <p>Incompatible SDK for ARC in target ApplicationName: macosx10.10</p>
  
  <p>Everything works and compiles, but still warning.  The code is mixed swift and objective C, with ARC.  Anyone else had this issue?</p>