title: Recurring error on xcode 5: file .h has been modified since the precompiled header .pcm was built
body: <p>This is the error I get:</p>
  
  <pre><code>fatal error: file '/Applications/Xcode 2.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS7.0.sdk/System/Library/Frameworks/AssetsLibrary.framework/Headers/ALAssetRepresentation.h' has been modified since the precompiled header '/Users/user/Library/Developer/Xcode/DerivedData/ModuleCache/16ZE17LEJCX4P/AssetsLibrary.pcm' was built
  note: after modifying system headers, please delete the module cache at '/Users/user/Library/Developer/Xcode/DerivedData/ModuleCache/16ZE17LEJCX4P'
  1 error generated.
  </code></pre>
  
  <hr>
  
  <p>So the problem is that these system .h files(ALAssetRepresentation.h in this error) get modified(not by me, at least not knowingly), I see in the finder that their modified date has been changed, and the only way to solve it is to copy them from another my old xcode directory(xcode4), as it still preserves the old modified date.</p>
  
  <p>Does anyone have a hint on why these files get modified and how to prevent it? I can change them to read only but I fear that this change might just screw things even more(having a write permissions seems to the default, I've checked with other people's installations).</p>
  
  <p>Thanks</p>