Currently, the WebMap Silverlight framework does not support any kind of script optimization in production mode, due to a limitation on the current state of the framework. Even though it is possible to configure a webpack.config.js, this will not be reflected because on the angular.json the script optimization explicitly has to be set to false so the framework can work as expected.
angular.json
{..."optimization":{"scripts":false}...}
Here is a list of useful documentation to properly understand the Angular optimization process.