$ sudo ln -s /Applications/Xcode_7.3.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk /Developer/SDKs/
MacOs/ 10:50:09 $ sudo ln -s /Applications/Xcode_8.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk /Developer/SDKs/
MacOs/ 10:51:34 $ sudo ln -s /Applications/Xcode_8.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk /Developer/SDKs/
$ sudo xcode-select -switch /Applications/Xcode_7.3.1.app/Contents/Developer/
$ xcode-select -p
/Applications/Xcode_7.3.1.app/Contents/Developer