React Native Fix Xcode 11 build

Xcode 11 build React Native 0.49.5 报错

020-06-28 15:12:27.000 [error][tid:main][RCTModuleMethod.mm:362] 
Unknown argument type '__attribute__' in method 
-[RCTAppState getCurrentAppState:error:]. Extend RCTConvert to support this type.

修复方法

React/Base/RCTModuleMethod.mm

static BOOL RCTParseUnused(const char **input)
{
  return RCTReadString(input, "__attribute__((unused))") ||
       +  RCTReadString(input, "__attribute__((__unused__))") ||
         RCTReadString(input, "__unused");
}