Currently the Python wheel build process must re-build Boost from source on every invocation, which takes a long time. It seems like we could combine the /host mount in cibuildwheel (https://cibuildwheel.pypa.io/en/stable/faq/#linux-builds-in-containers) with https://github.com/actions/cache (see also https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows) to build Boost once per (Python version, platform), then load this instead of rebuilding. Not 100% sure how to tell the cibuildwheel action to interact with cache, though.