TARGET_OS_WIN32           - Generated code will run under 32-bit Windows
TARGET_OS_UNIX            - Generated code will run under some Unix (not OSX) 
TARGET_OS_MAC             - Generated code will run under Mac OS X variant/对于（可能）在Apple平台上运行的任何Cocoa应用程序，TARGET_OS_MAC将为1。
   TARGET_OS_OSX          - Generated code will run under OS X devices
   TARGET_OS_IPHONE          - Generated code for firmware, devices, or simulator
      TARGET_OS_IOS             - Generated code will run under iOS 
      TARGET_OS_TV              - Generated code will run under Apple TV OS
      TARGET_OS_WATCH           - Generated code will run under Apple Watch OS
      TARGET_OS_BRIDGE          - Generated code will run under Bridge devices
   TARGET_OS_SIMULATOR      - Generated code will run under a simulator
TARGET_OS_EMBEDDED        - DEPRECATED: Use TARGET_OS_IPHONE and/or
TARGET_OS_SIMULATOR instead
TARGET_IPHONE_SIMULATOR   - DEPRECATED: Same as TARGET_OS_SIMULATOR
TARGET_OS_NANO            - DEPRECATED: Same as TARGET_OS_WATCH