build: `guix` package was removed from debian

[laanwj]

Apparently the guix debian package was no longer maintained, and was removed from debian recently (see https://lwn.net/Articles/1035491/). Ubuntu and other debian derivatives will likely follow.

This means we need new setup instructions for guix on debian in contrib/guix/INSTALL.md.

[fanquake]

Related discussion in #33574.

[laanwj]

Thanks! Strange that i've not noticed before. This was the first time i ran into the issue.

For most platforms we could refer to the binary installers in https://ftp.gnu.org/gnu/guix/ .

It's mainly annoying on riscv64, because GUIX doesn't ship their own binaries for that, and debian did.

[laanwj]

A 1.5.0 release is planned for sometime in January 2026: https://codeberg.org/guix/release-planning/wiki/release-1.5.0-project/. So hopefully the situation is going to improve in future.

"Wait for 1.5.0" SGTM, too.

If it isn't re-added i think it makes sense to remove the mention of the package from the docs completely, as most people are bound to run the newest debian release. The wording of "various releases" is a bit vague, more people are likely going to run into this.

So let's keep this issue open until it's resolved one way or another.