build: gate utilities by target support

[xtqqczze]

Fix some compile errors on non-Unix platforms, failing pre-commit check

Related: #11019

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tail/tail-n0f (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/seq/seq-epipe is now passing!

[codspeed-hq]

Merging this PR will not alter performance

✅ 38 untouched benchmarks
⏩ 332 skipped benchmarks¹

---

_{Comparing xtqqczze:not-supported-target (1fc7d1b) with main (80cc829)²}

Footnotes

1. 332 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 (47d7c76) during the generation of this report, so 80cc829 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[oech3]

I don't like this solution. This is already covered by feature.

[xtqqczze]

I would like to get cargo clippy --workspace --all-targets --all-features working.

[oech3]

It does not making a sense to clippy unsupported part.

[oech3]

At least, I think distributor does not want to distribute stubs if Mafefile included a bug someday. compile_error! is better behavior for distributors.

[oech3]

You should ask upstream to auto-skip clippy when compile_error! appear.
Stub should not be distributed accidentaly anyway.

[oech3]

rust-lang/cargo#1197

[xtqqczze]

We already use supports stubs for chcon and runcon: #8795

[oech3]

People on MSYS2 could try to replace system binary with main's binary, or replace cygwin binary with windows binary if cygpath is not an issue. In the case, people can incorrectly override proper nohup.exe by stub nohup.exe and break the system. (*con are accidentally exception since MSYS does not have them. But we should not have)

[xtqqczze]

I guess we could avoid stubs with:

#![cfg_attr(not(unix), no_main)]
#![cfg(unix)]
uucore::bin!(uu_nohup);

Then we get a linker error, but at least no compile errors.

[oech3]

How about just removing compile_error!?

[xtqqczze]

The crate fails compile for non-Unix, so it seems the only options are to use a stub, linker error, or compile error.

[oech3]

I passed cargo check -p uu_true with #![no_main] only. So it looks best solution.

[oech3]

I'll investigate what I can do for bin! macro itself.

[oech3]

not(clippy)

[xtqqczze]

not(clippy)

Doesn't help for compile errors, e.g. with cargo check.

[oech3]

Linker error should happen also for multicall-call binary.

[xtqqczze]

Linker error should happen also for multicall-call binary.

How can I test this?

[oech3]

cargo check --no-default-features --features nohup

[oech3]

stdbuf is supported on Windows now (very limited).