【修改】ping 命令对于 IPv6 支持的判断

Signed-off-by: chenyong <1521761801@qq.com>

ping/ping.c

@@ -108,6 +108,8 @@ static err_t ping_send(int s, ip_addr_t *addr, int size)
     to.sin_addr.s_addr = addr->u_addr.ip4.addr;
 #elif LWIP_IPV4
     to.sin_addr.s_addr = addr->addr;
+#elif LWIP_IPV6
+#error Not supported IPv6.
 #endif
 
     err = lwip_sendto(s, iecho, ping_size, 0, (struct sockaddr*) &to, sizeof(to));