dirname: add fuzzer to test GNU compatibility

[sylvestre]

No description provided.

[sylvestre]

it should not identify any crash
it is really for compat
should pass after #8936 is merged

[codspeed-hq]

Merging this PR will improve performance by 37.71%

⚡ 8 improved benchmarks
✅ 274 untouched benchmarks
⏩ 38 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Memory	sort_mixed_data[500000]	27.1 MB	22.9 MB	+18.63%
⚡	Memory	sort_numeric[500000]	79.2 MB	75.5 MB	+4.89%
⚡	Memory	sort_accented_data[500000]	28.3 MB	22.1 MB	+27.86%
⚡	Memory	sort_case_sensitive[500000]	17.4 MB	16.9 MB	+3.02%
⚡	Memory	sort_long_line[160000]	981.4 KB	712.6 KB	+37.71%
⚡	Memory	sort_unique_locale[500000]	39.8 MB	33.6 MB	+18.36%
⚡	Memory	sort_key_field[500000]	51.8 MB	47.8 MB	+8.24%
⚡	Memory	sort_ascii_only[500000]	28.3 MB	22.2 MB	+27.82%

---

_{Comparing sylvestre:dirname-fuzz (bf7ca75) with main (571e139)²}

Footnotes

1. 38 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. ↩

2. No successful run was found on main (b3ad96f) during the generation of this report, so 571e139 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[sylvestre]

nice, it fails as expected

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/follow-name. tests/tail/follow-name is passing on 'main'. Maybe you have to rebase?