It keeps saying:
fatal error: file '/Applications/Xcode5-DP5.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS7.0.sdk/usr/include/objc/NSObject.h'
has been modified since the precompiled header
'/Users/jackiexu/Library/Developer/Xcode/DerivedData/ModuleCache/2MWVPCGUMQ29P/ObjectiveC.pcm' was built
note: after modifying system headers, please delete the module cache at '/Users/jackiexu/Library/Developer/Xcode/DerivedData/ModuleCache/2MWVPCGUMQ29P'
1 error generated.
I must have deleted the derived data at least five times by now, and I'm getting nowhere. Any ideas?
Open a terminal and type in : rm -rf ~/Library/Developer/Xcode/DerivedData/ModuleCache/*
Clean your project and build again. Worked for me.