scx_utils: use c_char to prevent build failures

Use c_char to convert C strings, that is more portable across different
architectures.

This prevents a build failure on arm64 and ppc64el.

Fixes: d57a23f ("rust/scx_utils: Add user_exit_info support")
Signed-off-by: Andrea Righi <[email protected]>

Author: Andrea Righi

rust/scx_utils/src/user_exit_info.rs

@@ -6,6 +6,7 @@ use crate::bindings;
 use anyhow::bail;
 use anyhow::Result;
 use std::ffi::CStr;
+use std::os::raw::c_char;
 
 pub enum ScxExitKind {
     None = bindings::scx_exit_kind_SCX_EXIT_NONE as isize,
@@ -71,9 +72,9 @@ impl UserExitInfo {
     /// type which then calls this method with the individual fields.
     pub fn new(
         kind_ptr: *const i32,
-        reason_ptr: *const i8,
-        msg_ptr: *const i8,
-        dump_ptr: *const i8,
+        reason_ptr: *const c_char,
+        msg_ptr: *const c_char,
+        dump_ptr: *const c_char,
     ) -> Self {
         let kind = unsafe { std::ptr::read_volatile(kind_ptr) };