I don't think "built modules" is as intuitive to users as "loaded modules", even though there's a technical backstory to that naming.
Created dedicated file builder for building separate, compressed JS modules under temp. Updated the file builder for JS modules to now use either JS modules or compressed JS modules under temp. Updated the file builder for in-memory built size to base its size on the new compressed JS modules under temp, rather than the built JS modules that can either be compressed or not, depending on the isDev config option.