This is a hack to get core binaries into a container using pack so it can be deployed on Toolforge.
It is slightly less terrible than the previous solution of dumping the pre-compiled binary onto NFS then executing it in a container.
Once T401075 / T363027 is resolved, this can be replaced.
setup.pyhandles setting up the container image (downloading the binary)
$ pack build --builder heroku/builder:24 external-core