Use the correct cvt for converting socket errors on Windows.

`WSADuplicateSocketW` returns 0 on success, which differs from
handle-oriented functions which return 0 on error. Use `sys::net::cvt`
to handle its return value, which handles the socket convention of
returning 0 on success, rather than `sys::cvt`, which handles the
handle-oriented convention of returning 0 on failure.

Author: sunfishcode

library/std/src/os/windows/io/socket.rs

@@ -8,6 +8,7 @@ use crate::io;
 use crate::marker::PhantomData;
 use crate::mem;
 use crate::mem::forget;
+use crate::sys;
 use crate::sys::c;
 use crate::sys::cvt;
 
@@ -80,7 +81,7 @@ impl OwnedSocket {
         let result = unsafe {
             c::WSADuplicateSocketW(self.as_raw_socket(), c::GetCurrentProcessId(), &mut info)
         };
-        cvt(result)?;
+        sys::net::cvt(result)?;
         let socket = unsafe {
             c::WSASocketW(
                 info.iAddressFamily,