Add shared heap sample (#3806)

samples/shared-heap/wasm-apps/test2.c

@@ -0,0 +1,18 @@
+/*
+ * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include <stdio.h>
+
+#include <stdio.h>
+
+extern void
+shared_free(void *ptr);
+
+void
+print_buf(char *buf)
+{
+    printf("wasm app2's wasm func received buf: %s\n\n", buf);
+    shared_free(buf);
+}