Removing files from a broccoli tree with ember-cli-build

I am working on an Ember.js project in my company, we are using Ember.js for some time now. Currently we are developing a product, which has different "versions" for different clients, meaning that the .css files (and also some functionality) changes according to environmental settings.

Now, what I want to do is remove some style definition files from the broccoli tree in the ember-cli-build.js file so that the compiled app.css wouldn't contain the unnecessary lines. For that purpose I need to remove some lines from (the original, uncompiled) main app.css which I could manage to do with broccoli-replace, but I also need to remove complete files or directories and when it comes to that, I fail.

I've looked for an answer and found the broccoli-file-remover tool which looked just right to me for the job but unfortunately I couldn't get it to work and the examples online are always about what should be put in Brocfile.js, nothing about the implementation in ember-cli-build.js.

I did try to look for an answer before asking a new question here, I even tried and asked the "smartest guy" in the office but with little success. I would copy my code here but I don't really think it's needed as what I need is the simplest working example, where given an app/styles/test_folder/ folder the framework removes that folder during build so the final compiled files (either it's a .css or a .js) wouldn't contain any content that was originally in that folder.

PS First I wanted to comment to other, related questions but without the reputation I am not able to do that, hence the new thread. :(