I'm behind a proxy, so I was getting this error when I ran "sudo make build":
Cloning into 'heroku-buildpack-multi'...
fatal: unable to access 'https://github.com/ddollar/heroku-buildpack-multi.git/': Failed to connect to github.com port 443: Connection timed out
The solution? Replace the Dockerfile in the root of the folder you git cloned with this: