Build failed after modifying the git submodules

[Jeffwan]

Related code change: #14. commit is changed and it failed to find it from upstream

[Jeffwan]

Since we do not own upstream repo and we can not push submodule to remote, It failed to find the detached commit.
After some exploration, I can not find a way to make it. Instead, I'd like to clone a downstream repo and still use git submodule to mange it