env: apply --ignore/--default/--block-signal to real-time signals

[sylvestre]

Should make test tests/env/env-signal-handler.sh pass

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/symlink (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/env/env-signal-handler is no longer failing!
Note: The gnu test tests/tail/tail-n0f is now being skipped but was previously passing.
Note: The gnu test tests/unexpand/bounded-memory is now being skipped but was previously passing.

[codspeed-hq]

Merging this PR will degrade performance by 3.42%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 1 regressed benchmark
✅ 322 untouched benchmarks
⏩ 46 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	echo_consecutive_calls	121.7 µs	126 µs	-3.42%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing sylvestre:env-timeout-rtsignals (3eb6e0d) with main (b2ddbab)²}

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. ↩

2. No successful run was found on main (758791a) during the generation of this report, so b2ddbab was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩