Take sys/vxworks/stack_overflow from sys/unix instead.

library/std/src/sys/unix/stack_overflow.rs

@@ -219,7 +219,7 @@ pub unsafe fn drop_handler(handler: &mut Handler) {
     target_os = "solaris",
     target_os = "illumos",
     all(target_os = "netbsd", not(target_vendor = "rumprun")),
-    target_os = "openbsd"
+    target_os = "openbsd",
 )))]
 mod imp {
     pub unsafe fn init() {}

library/std/src/sys/vxworks/mod.rs

@@ -28,6 +28,7 @@
 pub mod rand;
 #[path = "../unix/rwlock.rs"]
 pub mod rwlock;
+#[path = "../unix/stack_overflow.rs"]
 pub mod stack_overflow;
 pub mod stdio;
 pub mod thread;

library/std/src/sys/vxworks/stack_overflow.rs

@@ -1,38 +0,0 @@
-#![cfg_attr(test, allow(dead_code))]
-
-use self::imp::{drop_handler, make_handler};
-
-pub use self::imp::cleanup;
-pub use self::imp::init;
-
-pub struct Handler {
-    _data: *mut libc::c_void,
-}
-
-impl Handler {
-    pub unsafe fn new() -> Handler {
-        make_handler()
-    }
-}
-
-impl Drop for Handler {
-    fn drop(&mut self) {
-        unsafe {
-            drop_handler(self);
-        }
-    }
-}
-
-mod imp {
-    use crate::ptr;
-
-    pub unsafe fn init() {}
-
-    pub unsafe fn cleanup() {}
-
-    pub unsafe fn make_handler() -> super::Handler {
-        super::Handler { _data: ptr::null_mut() }
-    }
-
-    pub unsafe fn drop_handler(_handler: &mut super::Handler) {}
-}