If you have multiple Xcode installations you may choose which toolset Appium should use with one of two ways:
Only available with sudo privileges, affects the whole system.
Assuming you want to choose /Applications/Xcode7.app: 1. Set default Xcode. sudo xcode-select -s /Applications/Xcode7.app/Contents/Developer 2. Run Appium (from command line or with GUI). appium
No privileges needed, affects only the current shell, so Appium should be started within that shell.
Assuming you want to choose /Applications/Xcode9.app: 1. Set DEVELOPER_DIR environment variable. export DEVELOPER_DIR=/Applications/Xcode9.app/Contents/Developer 2. Run Appium from the same shell. appium