don't manually cast to self i32 type

src/system/syscall.rs

@@ -188,7 +188,7 @@ pub type SignalHandler = extern "C" fn(c_int);
 
 pub fn signal(signal: i32, handler: SignalHandler) -> Result<()> {
     #[allow(clippy::single_match)]
-    match unsafe { libc::signal(signal as i32, handler as libc::sighandler_t) } {
+    match unsafe { libc::signal(signal, handler as libc::sighandler_t) } {
         libc::SIG_ERR => ctx_os_error(format_args!("invalid handler for {signal:?}")),
         _ => Ok(()),
     }