Fix unreachable_pub lint for hermit target

[thaliaarchi]

The build for the hermit target (#[cfg(target_os = "hermit")]) fails on master as of 8df89d1cb07 (2025-02-05), due to introducing #[warn(unreachable_pub)] at the root in #134286 (Enable unreachable_pub lint in core, merged 2025-01-20).

Make the relevant visibility modifiers more specific to resolve the warning.

$ ./x build --target x86_64-unknown-hermit
Building bootstrap
    Finished `dev` profile [unoptimized] target(s) in 0.34s
Building stage0 library artifacts (x86_64-apple-darwin)
    Finished `release` profile [optimized] target(s) in 0.15s
Building compiler artifacts (stage0 -> stage1, x86_64-apple-darwin)
    Finished `release` profile [optimized] target(s) in 1.67s
Creating a sysroot for stage1 compiler (use `rustup toolchain link 'name' build/host/stage1`)
Building stage1 library artifacts {alloc, core, panic_abort, panic_unwind, proc_macro, std, sysroot, test, unwind} (x86_64-apple-darwin -> x86_64-unknown-hermit)
   Compiling panic_unwind v0.0.0 (library/panic_unwind)
error: unreachable `pub` item
  --> library/panic_unwind/src/hermit.rs:10:9
   |
10 |         pub fn __rust_abort() -> !;
   |         ---^^^^^^^^^^^^^^^^^^^^^^^^
   |         |
   |         help: consider restricting its visibility: `pub(crate)`
   |
   = help: or consider exporting it for use by other crates
   = note: `-D unreachable-pub` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(unreachable_pub)]`

error: unreachable `pub` item
  --> library/panic_unwind/src/hermit.rs:17:9
   |
17 |         pub fn __rust_abort() -> !;
   |         ---^^^^^^^^^^^^^^^^^^^^^^^^
   |         |
   |         help: consider restricting its visibility: `pub(crate)`
   |
   = help: or consider exporting it for use by other crates

error: could not compile `panic_unwind` (lib) due to 2 previous errors
Build completed unsuccessfully in 0:00:39

[rustbot]

r? @joboet

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[thaliaarchi]

r? @Noratrieb, since you helped triage it

[Noratrieb]

@bors r+ rollup thanks!

[bors]

📌 Commit 5794952 has been approved by Noratrieb

It is now in the queue for this repository.