How to merge two JS files with their source-map?

Question

JavaScript

Hello. There are two js files, each with its own map file. The files are compiled by Webpack.
The first file is dependencies. This file is only rebuilt when the list of dependencies changes. The second is the Angular application itself. Rebuilt every time the code changes.
After compilation, I want to glue them into one file so that I can trace the application code with a debugger.
Already tried:
mapcat - Ran into a problem - https://github.com/edc/mapcat/issues/12
UglifyJS2 - Not sure if two source-maps can be specified - https://github.com/mishoo/UglifyJS2/ issues/2419
I also tried other solutions, which turned out to be either not working, or when starting the debugger, they show the code in the glued files, and not the source ones.