fix clippy

Author: loongs-zhang

core/src/coroutine/korosensei.rs

@@ -7,6 +7,8 @@ use crate::{catch, warn};
 use corosensei::stack::{DefaultStack, Stack};
 use corosensei::trap::TrapHandlerRegs;
 use corosensei::CoroutineResult;
+#[cfg(all(any(target_os = "linux", target_os = "android"), target_arch = "x86"))]
+use num_conv::CastSigned;
 use std::cell::{Cell, RefCell, UnsafeCell};
 use std::collections::VecDeque;
 use std::ffi::c_longlong;