Hi @brandonscott, using the suggestion from @mackstar, I create this custom buildpack.
https://github.com/krlsdu/heroku-buildpack-java
and
https://github.com/krlsdu/heroku-buildpack-jvm-common
and update on gitlabci the variable
BUILDPACK_URL=GitHub - krlsdu/heroku-buildpack-java: A Heroku buildpack for Java apps.
Obs.: This repository is designed for experimentation and will not be updated.