lwip: Support for linux target

Implement linux port layer and reuse the original FreeRTOS layer
that's compiled and used on linux target as well, by means of FreeRTOS
simulator.

components/lwip/test_afl_host/esp_attr.h

@@ -1,10 +1,2 @@
 #pragma once
-#define _ESP_NETIF_SUPPRESS_LEGACY_WARNING_
-#define __ARCH_CC_H__
-#define __XTENSA_API_H__
 #define IRAM_ATTR
-#define FLAG_ATTR(TYPE)
-#define SSIZE_MAX INT_MAX
-#undef assert
-#define assert(x)
-#define sys_prot_t int