工程报如下错误：
fatal error: file ‘/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/
Developer/SDKs/iPhoneSimulator8.0.sdk/usr/include/sysexits.h‘ has been modified since the
precompiled header ‘/Users/Lycros/Library/Developer/Xcode/DerivedData/ModuleCache/NZL05J5PKZ6B/
***.pch.pch‘ was built
解决方式如下：
Quit Xcode and remove everything in the module cache located here:
~/Library/Developer/Xcode/DerivedData/ModuleCache （删除该文件中的缓存即可）
The cache that was built with a previous version of Xcode is invalid for this version of Xcode and SDK, and that is causing your error
如果不小心修改了系统SDK文件，编译无法通过改怎么办？（iOS开发）
原文：http://blog.csdn.net/u011344883/article/details/41958525
