Command Line Tools

1. xcode-select –install
   xcode-select–install 实际上是启动了 /System/Library/CoreServices/Install Command Line DeveloperTools.app 应用，该应用从Apple服务器上下载「CLToolsExecutables.pkg」和「MacOSX109_SDK.pkg」执行安装。

2. https://developer.apple.com/ 下载

gcc -v命令查看是否安装成功

安装在mac的根目录中
/Library/Developer/CommandLineTools/

ld: unsupported tapi file type ‘!tapi-tbd’ in YAML file
library not found for -lstdc++.6.0.9

Xcode10:
    /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/

Xcode11 beta
/Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib 
/Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib/
/Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/lib/
/Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/lib/