Greetings! I've written a brief blog that describes how Wikimedia uses optional build steps as an enhancement to ResourceLoader and our evolving pipeline. If you use ResourceLoader in your projects, you may find it helpful:

https://phabricator.wikimedia.org/phame/post/view/206/all_code_is_built/

Thank you to the following reviewers for their great feedback: Jan Drewniak, Santhosh Thottingal, Daniel Cipoletti, Joe Walsh, Bernd Sitzmann, and Mónica Pinedo Bajo.

Stephen