libs/libc/netdb/lib_dnsbind.c: Make DNS recevie timeout configurable.

libs/libc/netdb/Kconfig

@@ -54,6 +54,13 @@ menuconfig NETDB_DNSCLIENT
 
 if NETDB_DNSCLIENT
 
+config NETDB_DNSCLIENT_RECV_TIMEOUT
+	int "DNS receive tiemout"
+	default 30
+	---help---
+		This the timeout value when DNS receive response after
+		dns_send_query, unit: seconds
+
 config NETDB_DNSCLIENT_ENTRIES
 	int "Number of DNS resolver entries"
 	default 0 if DEFAULT_SMALL

libs/libc/netdb/lib_dnsbind.c

@@ -107,7 +107,7 @@ int dns_bind(void)
 
   /* Set up a receive timeout */
 
-  tv.tv_sec  = 30;
+  tv.tv_sec  = CONFIG_NETDB_DNSCLIENT_RECV_TIMEOUT;
   tv.tv_usec = 0;
 
   ret = setsockopt(sd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(struct timeval));