Lua not available to subsequent build packs

Scenario: Using Node+Lua together with 

https://github.com/ddollar/heroku-buildpack-multi/ ->
https://github.com/nathanaeljones/heroku-buildpack-lua.git
https://github.com/heroku/heroku-buildpack-nodejs.git

And https://github.com/brettlangdon/NodeLua

After `heroku-buildpack-lua` completes, 'lua' is not available in the search path for `heroku-buildpack-nodejs` to successfully install NodeLua.
