问题：
Undefined symbols for architecture x86_64:
"_OBJC_CLASS_$_AWAdIntersitialManager", referenced from:
objc-class-ref in AWInterstitialVC.o
clang: error: linker command failed with exit code 1 (use -v to see invocation)
原因： 当我们复制或者新建文件的时候 AWAdIntersitialManager文件没有参与到工程编译，就会造成找不到AWAdIntersitialManager类，编译错误，
解决方案：在target -> Build Phases -> Compile Sources里面加入AWAdIntersitialManager.m文件重新编译