statfs: Fix definitions for s390x musl with libc 0.2.176

[Gelbpunkt]

What does this PR do

This PR fixes compilation against libc 0.2.176 on s390x-unknown-linux-musl. libc 0.2.176 fixed the definitions of statfs to align them with musl, see rust-lang/libc#4549 for the PR that fixed it.

I'm not sure why libc is currently pinned to 0.2.175, but I tested this locally against 0.2.176 on s390x-unknown-linux-gnu and s390x-unknown-linux-musl and the statfs code compiles fine for both now.

Checklist:

• I have read CONTRIBUTING.md
• I have written necessary tests and rustdoc comments
• A change log has been added if this PR modifies nix's API

[neuschaefer]

What does this PR do

This PR fixes compilation against libc 0.2.176 on s390x-unknown-linux-musl. libc 0.2.176 fixed the definitions of statfs to align them with musl, see rust-lang/libc#4549 for the PR that fixed it.

I'm not sure why libc is currently pinned to 0.2.175, but I tested this locally against 0.2.176 on s390x-unknown-linux-gnu and s390x-unknown-linux-musl and the statfs code compiles fine for both now.

The PR description (at least the first paragraph) might be worth having in the git history (i.e. in the commit message)

[Kladki]

Closes #2683

[sertonix]

Is there anything blocking this MR?

[omnivagant]

it would be really nice to get this in so that we don't have to do things like https://git.alpinelinux.org/aports/commit/?id=19c85d09fa13f75669dc464c4dc14484eb0df6ee

[sertonix]

@SteveLauC Could you take a look at this, please?

[SteveLauC]

I just rebased your branch to re-run CI, since I couldn’t find the re-run button for the previous run, it was too old.

[SteveLauC]

The PR description (at least the first paragraph) might be worth having in the git history (i.e. in the commit message)

Nix doesn’t include the PR description in the commit message, so I manually ran git commit --amend to include it.

[sertonix]

Thanks!