sort: replace nix feature resource with rustix

[xtqqczze]

Avoid compiling the nix feature resource.

[oech3]

I guess libc is still dep of rustix on non-Linux.

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/misc/io-errors. tests/misc/io-errors is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/tail/tail-n0f (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/pr/bounded-memory (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/printf/printf-surprise is now passing!

[xtqqczze]

I guess libc is still dep of rustix on non-Linux.

libc is only a direct dependency because we use it in current_open_fd_count.

[xtqqczze]

GnuTests / Aggregate GNU test results (pull_request) failure tracked by #12277.

[cakebaker]

Thanks!