uucore: perms imports safe_traversal unconditionally, breaking aix/hurd/redox builds

Summary

uucore's perms feature enables safe-traversal, and perms.rs imports it unconditionally:

// src/uucore/src/lib/features/perms.rs:32
use crate::features::safe_traversal::{DirFd, SymlinkBehavior};

But the module itself is compiled only for a subset of unix:

// src/uucore/src/lib/features.rs:88-93  (and lib.rs:106-111)
#[cfg(all(
    feature = "safe-traversal",
    unix,
    not(any(target_os = "aix", target_os = "hurd", target_os = "redox"))
))]
pub mod safe_traversal;

So on aix, hurd and redox, any crate that enables uucore/perms fails to build:

error[E0432]: unresolved import `crate::features::safe_traversal`
  --> src/uucore/src/lib/features/perms.rs:32:22
   |
32 | use crate::features::safe_traversal::{DirFd, SymlinkBehavior};
   |                      ^^^^^^^^^^^^^^ could not find `safe_traversal` in `features`

chmod, chown, chgrp, chcon, runcon, cp, mv and install all enable perms.

Why it matters for Redox specifically

feat_os_unix_redox includes chmod (Cargo.toml:371-377), and uu_chmod enables uucore/perms. So the documented Redox feature set does not build.

Why it has gone unnoticed

The Redox CI job is commented out:

# .github/workflows/CICD.yml:388
# - { os: ubuntu-latest, target: x86_64-unknown-redox, features: feat_os_unix_redox, use-cross: redoxer, skip-tests: true, check-only: true }

Reproducing without a Redox toolchain

Add target_os = "linux" to the exclusion list in both features.rs and lib.rs, then cargo build -p uu_chmod. The same E0432 appears.

Suggested fix

Either gate the perms.rs import and its uses on the same cfg as the module and provide a fallback for those targets, or widen safe_traversal to compile on them. Re-enabling the Redox check-only job afterwards would stop it regressing.

Start by comparing the cfg declarations in src/uucore/src/lib/features.rs and lib.rs with the import and uses in src/uucore/src/lib/features/perms.rs. Reproduce the failure with the documented cfg change and cargo build -p uu_chmod, then inspect Cargo.toml and .github/workflows/CICD.yml; done means the affected target configuration builds and the Redox check-only job can be re-enabled without regression.