Install docker. For OSX, I recommend using dvm to get virtualbox, vagrant and boot2docker set up correctly.
Build:
$ cd support
$ docker build -t your-username/postgresql-builder .
$ docker run -i -v /home/docker/cache:/var/cache \
-e POSTGRESQL_VERSION=<postgresql-version> \
-e AWS_ACCESS_KEY_ID=<ur-key> \
-e AWS_SECRET_ACCESS_KEY=<ur-secret-key> \
-e S3_BUCKET="gregburek-buildpack-postgresql" \
your-username/postgresql-builder
heroku plugins:install https://github.com/heroku/heroku-buildpacks
cd heroku-buildpack-postgresql
git checkout master
heroku buildpacks:publish gregburek/postgresql