sync: replace nix by rustix

[oech3]

split #11548
Adding libc... but no additional unsafe.

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/misc/sync. tests/misc/sync is passing on 'main'. Maybe you have to rebase?
Skipping an intermittent issue tests/tail/inotify-dir-recreate (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/dd/no-allocate is now being skipped but was previously passing.
Note: The gnu test tests/rm/many-dir-entries-vs-OOM is now being skipped but was previously passing.
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.
Congrats! The gnu test tests/printf/printf-surprise is now passing!

[oech3]

GNU test failed: tests/misc/sync. tests/misc/sync is passing on 'main'. Maybe you have to rebase?

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/misc/sync. tests/misc/sync is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/date/date-locale-hour (passes in this run but fails in the 'main' branch)