每次重装环境xcode都提示缺少文件，并且网上搜到的都是只有一个libstdc++.6.0.9，找的比较麻烦，现在把缺少的libstdc都上传到GitHub上，方便下载
把文件复制到以下四个目录即可
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/Library/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib/
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/lib/
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/lib/
下载链接：
https://github.com/zhongjianfeipqy/Xcode10-libstdc
