For building precompiled binaries on non-x86_64 architectures in CI we need to ensure that all the python build dependencies have wheels already on those platforms. Otherwise we can end up in a situation where we are trying to build everything from source in a single job which might take far too long. This repo contains Dockerfiles to build images to use for CI jobs that are intendend to build wheels with precompiled binaries on aarch64, ppc64le, and s390x (which are the platforms supported by Travis CI and the manylinux2014 docker images).