Heroku: Loading variables before slug compilation

There is a setting in heroku labs that will load the variables before slug compilation:

heroku plugins:install https://github.com/heroku/heroku-labs.git
heroku labs:enable user_env_compile -a myapp

Reference:

http://www.johnplummer.com/tools/heroku-precompiling-assets-enviroment-variables.html