- Checkout with submodules, otherwise the sdist won't include libjsonnet.h
- Install golang in the cibuildwheel build container.
- Skip musllinux build; it's not working for me.
- Skip Windows platform builds; they're not working for me.

It would be nice to get the other platforms working but I have already
spent hours on this and haven't succeeded yet. Previous go-jsonnet
releases on PyPI didn't have prebuilt wheel packages anyway, so it's
still strictly better to have some rather than none even if not all
platforms are covered.