Place SDKs in /Developer/SDKs
[Hint] In newer versions of Xcode the SDKs are integrated within the app: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs
Place SDKs in /Developer/SDKs
[Hint] In newer versions of Xcode the SDKs are integrated within the app: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs