rework structure

bare-metal-bsp/libwrap/stdlib/.gitignore

@@ -0,0 +1 @@
+/*.o

bare-metal-bsp/libwrap/stdlib/malloc.c

@@ -0,0 +1,17 @@
+/* See LICENSE for license details. */
+
+/* These functions are intended for embedded RV32 systems and are
+   obviously incorrect in general. */
+
+void* __wrap_malloc(unsigned long sz)
+{
+  extern void* sbrk(long);
+  void* res = sbrk(sz);
+  if ((long)res == -1)
+    return 0;
+  return res;
+}
+
+void __wrap_free(void* ptr)
+{
+}