ices/80125.rs: fixed with no errors

[github-actions]

Issue: rust-lang/rust#80125

type ExternCallback = extern "C" fn(*const u8, u32, str);

pub struct Struct(ExternCallback);

#[no_mangle]
pub extern "C" fn register_something(bind: ExternCallback) -> Struct {
    Struct(bind)
}

fn main() {}

=== stdout ===
=== stderr ===
warning: `extern` fn uses type `str`, which is not FFI-safe
 --> /home/runner/work/glacier/glacier/ices/80125.rs:1:23
  |
1 | type ExternCallback = extern "C" fn(*const u8, u32, str);
  |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
  |
  = help: consider using `*const u8` and a length instead
  = note: string slices have no C equivalent
  = note: `#[warn(improper_ctypes_definitions)]` on by default

warning: `extern` fn uses type `str`, which is not FFI-safe
 --> /home/runner/work/glacier/glacier/ices/80125.rs:6:44
  |
6 | pub extern "C" fn register_something(bind: ExternCallback) -> Struct {
  |                                            ^^^^^^^^^^^^^^ not FFI-safe
  |
  = help: consider using `*const u8` and a length instead
  = note: string slices have no C equivalent

warning: `extern` fn uses type `Struct`, which is not FFI-safe
 --> /home/runner/work/glacier/glacier/ices/80125.rs:6:63
  |
6 | pub extern "C" fn register_something(bind: ExternCallback) -> Struct {
  |                                                               ^^^^^^ not FFI-safe
  |
  = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
  = note: this struct has unspecified layout
note: the type is defined here
 --> /home/runner/work/glacier/glacier/ices/80125.rs:3:1
  |
3 | pub struct Struct(ExternCallback);
  | ^^^^^^^^^^^^^^^^^

warning: 3 warnings emitted

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