xcode4 自定义静态库的编译和使用
http://hi.baidu.com/lu_waiting/blog/item/8595ffd357eb85afa1ec9cdb.html

如果编译时出现如下错误：File /Users/wangwei/Documents/three20/src/Three20/http://www.cnblogs.com/Build/Products/Debug-iphonesimulator/libThree20.a depends on itself. This target might include its own product.
则打开Three20.xcodeproj。点击工程名Three20，在右边的列表中取消对libThree20.a的勾选。