buildspec.yml builds using Dockerfile.build to pull from apache airflow docker, installs our requirements, and uploads the container to the root organization's ECR.
Dockerfile is what the code pipeline will use to deploy into the various ECS clusters; see terraform-modules for the airflow ECS configuration used to deploy.
Note that this really isn't a fork of wmorin/docker-airflow anymore but I couldn't figure out how to wipe that out before I left.