slirp: Fix non blocking connect for w32

Signed-off-by: Stefan Weil <sw@weilnetz.de>
diff --git a/tcp_input.c b/tcp_input.c
index e4f7bba..af46e36 100644
--- a/tcp_input.c
+++ b/tcp_input.c
@@ -581,8 +581,13 @@
             goto cont_input;
         }
 
-        if ((tcp_fconnect(so) == -1) && (errno != EINPROGRESS) &&
-            (errno != EWOULDBLOCK)) {
+        if ((tcp_fconnect(so) == -1) &&
+#if defined(_WIN32)
+            socket_error() != WSAEWOULDBLOCK
+#else
+            (errno != EINPROGRESS) && (errno != EWOULDBLOCK)
+#endif
+        ) {
             u_char code = ICMP_UNREACH_NET;
             DEBUG_MISC(
                 (dfd, " tcp fconnect errno = %d-%s\n", errno, strerror(errno)));