unexpand: codegen-units=1

[oech3]

#10798 improved perfs. And...?

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/usage_vs_getopt (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/shuf/shuf-reservoir (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/sort/sort-stale-thread-mem (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/pr/bounded-memory is no longer failing!

[codspeed-hq]

Merging this PR will improve performance by 7.18%

⚡ 2 improved benchmarks
✅ 282 untouched benchmarks
⏩ 38 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	unexpand_large_file[10]	410.4 ms	382.9 ms	+7.18%
⚡	Simulation	unexpand_many_lines[100000]	195.8 ms	182.7 ms	+7.18%

---

_{Comparing oech3:patch-2 (5a826c2) with main (4bbd71f)}

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. ↩