ビルドしたら以下のエラーが出た。
file '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/AppKit.framework/Headers/NSWindowController.h' has been modified since the precompiled header was built
Cleanしてから再ビルドしたら直った。
参考：[Xcode] fatal error: file ‘xxx’ has been modified since the precompiled header was built 1 error generated. | CodeNote.net
