fix: avoid xattr on unsupported platforms

[xtqqczze]

The xattr crate enables a default feature for unsupported Unix platforms. That is, it builds on all Unix platforms but always fails at runtime on unsupported Unix platforms.

Disable the default features so xattr does not build on unsupported platforms.

Closes #14642
Closes #14647
Closes #14658

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/retry (fails in this run but passes in the 'main' branch)

[codspeed]

Merging this PR will not alter performance

✅ 97 untouched benchmarks
⏩ 320 skipped benchmarks¹

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_{Comparing xtqqczze:deps/xattr (c364534) with main (1aa8780)²}

Footnotes

1. 320 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 (9bab5f1) during the generation of this report, so 1aa8780 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[krosci]

Cutting OpenBSD is not the best solution.

Please see #14658 (comment)