(make_lshd_port): Check that IPV6_V6ONLY is defined

before trying to setsockopt it.

Rev: src/lshd.c:1.189

src/lshd.c

@@ -325,7 +325,7 @@ make_lshd_port(struct lshd_context *ctx, socklen_t addr_len, struct sockaddr *ad
   if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof (yes)) <0)
     werror("setsockopt SO_REUSEADDR failed: %e.\n", errno);
 
-#if WITH_IPV6
+#if WITH_IPV6 && defined (IPV6_V6ONLY)
   if (addr->sa_family == AF_INET6)
     {
       if (setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &yes, sizeof(yes)) < 0)