feat(linux): provide getrandom implementation for macOS

This makes getrandom(2) usable when compiling with IDF_TARGET=linux
on a macOS host.

components/linux/include/sys/random.h

@@ -0,0 +1,15 @@
+/*
+ * SPDX-FileCopyrightText: 2023 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#pragma once
+
+#include_next "sys/random.h"
+
+#if __APPLE__
+#include <stddef.h>
+
+int getrandom(void *buf, size_t buflen, unsigned int flags);
+
+#endif  // __APPLE__