This is a Heroku buildpack for running a single Makefile in the heroku directory of your project. It doesn’t do anything else, so to actually compile your app you should combine it with another buildpack (ex. python, node, etc.).
$ ls
heroku
.buildpacks
$ ls heroku
Makefile
$ heroku create --buildpack https://github.com/tomaratyn/heroku-buildpack-vendored-makefile
$ git push heroku master
...
-----> Heroku receiving push
-----> Fetching custom buildpack
-----> Found a Makefile
...
The buildpack will detect that your app has a Makefile in the heroku directory. It will call make to execute the default target.
Based on Pete Peen’s excellent heroku-buildpack-vendorbinaries.