Load iOS 6.1 SDK into XCode5

1. Find the SDK file, like iPhoneOS6.1.sdk, in your or your friend's older Xcode directory.
2. Sym link the old SDK to the new XCode5 app directory:
3. ln -s /Applications/Xcode4.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS6.1.sdk /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS6.1.sdk