Rollup merge of rust-lang#82500 - CDirkx:hermit-pipe, r=joshtriplett

Reuse `std::sys::unsupported::pipe` on `hermit`

Pipes are not supported on `hermit` and `hermit/pipe.rs` is identical to `unsupported/pipe.rs`. This PR reduces duplication between the two by doing the following on `hermit`:

```rust
#[path = "../unsupported/pipe.rs"]
pub mod pipe;
```

Author: JohnTitor

library/std/src/sys/hermit/mod.rs

@@ -32,6 +32,7 @@ pub mod mutex;
 pub mod net;
 pub mod os;
 pub mod path;
+#[path = "../unsupported/pipe.rs"]
 pub mod pipe;
 #[path = "../unsupported/process.rs"]
 pub mod process;