Diagnostics don't identify `cfg` condition on `use std::os::fd::OwnedFd;`

[joshtriplett]

Code

use std::os::fd::OwnedFd;

fn main() {}

Current output

/tmp/my-portable-project$ cargo +nightly build --target x86_64-pc-windows-gnu
   Compiling my-portable-project v0.1.0 (/tmp/my-portable-project)
error[E0432]: unresolved import `std::os::fd`
 --> src/main.rs:1:14
  |
1 | use std::os::fd::OwnedFd;
  |              ^^ could not find `fd` in `os`

For more information about this error, try `rustc --explain E0432`.
error: could not compile `my-portable-project` (bin "my-portable-project") due to previous error

Desired output

The output should include the additional information from #109005 identifying the relevant cfg, effectively telling the user that this only exists on unix or wasi, not windows.

Rationale and extra context

No response

Other cases

No response

Anything else?

No response

[joshtriplett]

cc @Nilstrieb