You can install any packages by using linuxbrew.
To use this buildpack, you should prepare a .buildpacks file that contains this buildpack url and your real buildpack url:
$ ls
.cellar
.buildpacks
...
$ cat .cellar
mecab
mecab-ipadic
$ cat .buildpacks
https://github.com/sunny4381/heroku-buildpack-linuxbrew.git
$ heroku create --buildpack https://github.com/heroku/heroku-buildpack-multi
$ heroku config:add LD_LIBRARY_PATH=/app/.linuxbrew/lib
$ git push heroku master
...
MIT