Oh, I guess Trickle is a pain to build on MacOS.
Throttled is another command line tool that should work, and it comes with a prebuilt binary. Check the README for instructions on installing. Download is here
http://www.intrarts.com/throttledcli.htmlThere is also Carrafix, but this seems to be a bit old. Still, it might work on recent MacOS.
http://www.carrafix.com/carrafix/carrafix.html