Does System.js builder support preserving of License Comments when minifying / uglifying?

Question

I have used r.js for years but I am moving to systemjs-builder. Is there a flag so I can have it preserve license comments at the top of the file like r.js used to with preserveLicenceComments: true?

My goal is the same, having all the 3rd party licenses at the top of the uglified file.

Answer 1

https://github.com/systemjs/builder/issues/329

Shows the answer which is undocumented.