Instructions in the Appcelerator Legacy CLI docs suggest setting up aliases. But these require manual adjustment when new versions are installed. This automacitally links to the latest legacy CLI.
LATEST_TI=$(ls -1 $HOME/Library/Application\ Support/Titanium/mobilesdk/osx/ | sort -r | head -1)
alias titanium.py="$HOME/Library/Application\ Support/Titanium/mobilesdk/osx/$LATEST_TI/titanium.py"
alias ios_builder="$HOME/Library/Application\ Support/Titanium/mobilesdk/osx/$LATEST_TI/iphone/builder.py"