How to get a docker image with PR toolchains?

It would be pretty awsome to get a docker image tag for every PR, specially when that is attached to an Evolution Proposal like Rebase: [ConstraintSystem] Ability to treat key path literal syntax as function type (Root) -> Value. by beccadax · Pull Request #23435 · apple/swift · GitHub

Does anybody have a docker build script that I can use to download a PR toolchain like the below?