basic fork foo, function itself is empty

kernel/syscall/skeleton.cc

@@ -392,7 +392,9 @@ bool reply(Vault& v, const void* buffer, size_t size) {
   return true;
 }
 
-
+int fork(Vault &vault, InterruptContext *user_context) {
+  return 0;
+}
 
 
   }  // namespace Skeleton