Fix build issue

features/lwipstack/lwip-sys/arch/cc.h

@@ -35,6 +35,7 @@
 #include <stdint.h>
 #include <stddef.h> /* for size_t */
 #include "mbed_toolchain.h"
+#include "lwipopts.h"
 
 #ifdef __cplusplus
 extern "C" {

features/lwipstack/lwipopts.h

@@ -71,7 +71,10 @@
 #error "Either IPv4 or IPv6 must be preferred."
 #endif
 
-#define LWIP_DEBUG                  MBED_CONF_LWIP_DEBUG_ENABLED
+#undef  LWIP_DEBUG
+#if MBED_CONF_LWIP_DEBUG_ENABLED
+#define LWIP_DEBUG                  1
+#endif
 
 #if NO_SYS == 0
 #include "cmsis_os2.h"