Add command to set Xcode tools

[adam-fowler]

Is your feature request related to a problem? Please describe.
Add command that displays selection of Xcode installed on system and then set DEVELOPER_DIR in build environment variables based off selection

Find Xcode's installed
mdfind "kMDItemCFBundleIdentifier == 'com.apple.dt.Xcode'"
Get version name from install
/usr/libexec/PlistBuddy -c "Print :CFBundleShortVersionString" ${XCODE}/Contents/Info.plist