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/port/linux/include/sys/fcntl.h

@@ -0,0 +1,12 @@
+/*
+ * SPDX-FileCopyrightText: 2022-2023 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#pragma once
+#ifdef LWIP_HDR_ESP_LWIPOPTS_H
+// ignore when included from lwipopts.h since lwip provides all necessary definitions
+#else
+// otherwise include system fcntl
+#include_next <sys/fcntl.h>
+#endif