EmberJS in-repo-addon not compiling CoffeeScript files

We are using in-repo-addons in our projects and I recently came across and issue when trying to switch over to CoffeeScript.

We've install CoffeeScript support through the recommended method ember install ember-cli-coffeescript and that works without an issue. The strangeness starts when trying to use CoffeeScript in the in-repo-addon.

Coffee files added under repo->test-support will compile without issue but anything in any other folder will not. I've tried just about everything under the sun and compared my project with others where coffee works with the repo.

Has anyone run into this type of issue before and if so, what steps should I take to resolve it?