uucore/build.rs: small refactoring

[cakebaker]

No description provided.

[xtqqczze]

I guess filter would be more idiomatic:

let system_locale = env
    .as_deref()
    .and_then(|s| s.split('.').next())
    .map(|s| s.replace('_', "-"))
    .filter(|s| !s.is_empty() && s != "en-US");

[cakebaker]

Yes, I agree. I added you as a co-author.

[xtqqczze]

In this case it's not worth the complexity, but in theory we could avoiding allocating for this kind of operation:

fn replace_underscores(s: &mut String) {
    // SAFETY:
    // '_' and '-' are both single-byte ASCII characters,
    // so this preserves UTF-8 validity and string length.
    unsafe {
        s.as_mut_vec()
            .iter_mut()
            .filter(|b| **b == b'_')
            .for_each(|b| *b = b'-');
    }
}

[oech3]

In this case it's not worth the complexity

build.rs is not a production.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/rm/isatty (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/date/resolution (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/tail/truncate is no longer failing!
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.
Congrats! The gnu test tests/cut/bounded-memory is now passing!
Skip an intermittent issue tests/tail/tail-n0f (was skipped on 'main', now failing)