Cross-compilation steps

Hello,
where can I find instructions for building a x86_64-unknown-linux-musl binary? tectonic-ci-support/cross-images/README.md seems to be outdated.

Error when following README.md

When following instructions in README.md, I run into this error message:

$ sudo docker build -t tectonic-cross-compiler:v1 dist/docker/x86_64-alpine-linux-musl/

[+] Building 0.0s (6/0)

ERROR: unable to prepare context: path "dist/docker/x86_64-alpine-linux-musl/" not found

To be more precise, I have a Rust program which uses Tectonic as a library. I want to create a x86_64-unknown-linux-musl binary which could run on any linux distro.

Thanks,
Skalick√Ĺ