uucore: embed system locale on cargo install

[WaterWhisperer]

This PR fixes issue #8594 .

Previously, binaries installed via cargo install would only embed the English (en-US) locale. This change modifies the uucore/build.rs script to detect the system's locale via the LANG environment variable at compile time. It embeds the corresponding locale file if it exists, in addition to the mandatory English (en-US) fallback.

Verification

I verified this fix by setting my system locale to French (export LANG=fr_FR.UTF-8), for which the yes utility has an existing translation.

1. Ran cargo build --package uu_yes.
2. Executed ./target/debug/yes --help.

The command correctly displayed the help text in French, confirming that the build script now successfully embeds the user's system locale.

Testing with a Chinese locale (zh_CN) correctly resulted in a fallback to English, as no Chinese translation file currently exists for the yes utility. This demonstrates the fallback mechanism is working as expected.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/stdbuf (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)

[sylvestre]

it would be nice to see if this could be checked by github action too :)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/stdbuf (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)

[WaterWhisperer]

Hi @sylvestre,

I noticed this PR was reviewed and all checks passed back in September. I see that issue #8594 is still open and @oech3 recently asked about the progress in the original issue thread.

Just wanted to check - is there anything else needed before merging? I'm happy to:

• Rebase on the current main branch if needed
• Add any additional tests or changes you'd like to see

Thanks for your time and feedback!

[sylvestre]

i just forgot, sorry
could you please the conflict and i will have a look right after :)
thanks

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[sylvestre]

about test, i would like a test in github action itself. Unit tests are nice but they don't always cover users needs.

.github/workflows/l10n.yml
to verify that it works as appropriate and we don't regress in the future.

thanks again :)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

[oech3]

@WaterWhisperer ping

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

[codspeed-hq]

CodSpeed Performance Report

Merging #8604 will improve performances by 2.25%

_{Comparing WaterWhisperer:embed-sys-locale (ad48a3a) with main (6cf5b06)}

Summary

⚡ 1 improvement
✅ 122 untouched
⏩ 5 skipped¹

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	du_max_depth_balanced_tree[(6, 4, 10)]	33 ms	32.3 ms	+2.25%

Footnotes

1. 5 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. ↩

[oech3]

env LANG=fr_FR.UTF-8 cargo build -p uu_yes and env LANG=fr_FR.UTF-8 ./target/debug/yes' --help was english while make built binary supporting french.