dircolors: remove unsafe

[oech3]

No description provided.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/pr/bounded-memory (was skipped on 'main', now failing)

[xtqqczze]

Good work. This is exactly the kind of unsafe worth removing. I think most uses of env::set_var and env::remove_var are unnecessary if we refactor the tests accordingly.

[oech3]

I think fn run_gnu_cmd can use Command::env to remove unsafes.

[xtqqczze]

Yeah, we should definitely do that instead of mutating the environment. Regardless of the unsafe aspect, mutating global environment state makes the code harder to reason about and can interfere with optimizations.