tail(test): Attempt to fix flaky tail pipe test by increasing byte count

[Xylphy]

This is an experiment to check if a larger byte count fixes the flaky test.

The test test_when_output_closed_then_no_broken_pie sometimes passes and sometimes fails because the pipe buffer size can hold the entire output before the parent closes stdout. That leads to a deferred flush error instead of an immediate write error, and fails_silently() sees output on stderr.

By increasing the argument from 100000 to 10000000 (10 MB), the pipe buffer will always fill up, forcing the error to occur during an active write() call where it can be silently suppressed.

• Issue: test_when_output_closed_then_no_broken_pie intermittent failure #13569
• Failure log: https://github.com/uutils/coreutils/actions/runs/30171537944/job/89713408493?pr=13568

Just testing if this works, if CI stays green / this test succeeds multiple times.

[codspeed-hq]

Merging this PR will improve performance by 3.02%

⚡ 1 improved benchmark
✅ 344 untouched benchmarks
⏩ 46 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	cksum_crc32b	40.9 ms	39.7 ms	+3.02%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing Xylphy:test/fix-flaky-broken-pipe-test (788fb90) with main (0c8a3c7)}

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:

Skip an intermittent issue tests/rm/isatty (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)
Skipping an intermittent issue tests/cut/bounded-memory (passes in this run but fails in the 'main' branch)