OC、C++、Swift混编易遇到如下问题：
Use of '@import' when C++ modules are disabled, consider using -fmodules and -fcxx-modul
解决：在target -> build settings -> Apple Clang - Custom Compiler Flags -> Other C++ Flags选项加上-fcxx-modulesCould Not build module 'xxx'，在xxx-swift.h中报错Include of non-modular header inside framework module 'xxx.Swift'
解决：target -> build settings -> Apple Clang - Language - Modules -> Allow Non-modular Includes in Framework modules设置为YES
