heroku-buildpack-multi
Use multiple buildpacks on your app
Usage
$ heroku config:add BUILDPACK_URL=https://github.com/ddollar/heroku-buildpack-multi.git
$ cat .buildpacks
https://github.com/heroku/heroku-buildpack-nodejs.git#0198c71daa8
https://github.com/heroku/heroku-buildpack-ruby.git