wc: introduce IS_POSIXLY_CORRECT static

[xtqqczze]

No description provided.

[codspeed-hq]

Merging this PR will not alter performance

✅ 309 untouched benchmarks
⏩ 46 skipped benchmarks¹

---

_{Comparing xtqqczze:static-posixly-correct (e82ce7c) with main (01b7177)}

Footnotes

1. 46 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/date/date-locale-hour (passes in this run but fails 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/timeout/timeout-group is no longer failing!

[Alonely0]

If the benches are so trivial that fetching an env var takes a 5% perf hit, they're not good benches lol. No it's CodSpeed running on a different environment lol. Ignore me.

[Alonely0]

Looks good to me :)

[Alonely0]

The new CodSpeed regressions are probably an LLVM thing from the recent update; it's unrelated to wc so I'd ignore it.

[xtqqczze]

The CodSpeed regressions disappeared with same runtime environment.