Remove usage of old build system

[4brunu]

Bridgecraft uses the legacy build system because the new one, doesn't support -dry-run. https://github.com/lvsti/Bridgecraft/blob/d047af14511440869a21ace4806eea9ad481ec8f/Bridgecraft/GenerateCommand.swift#L248 This isn't an issue right now, but it can be in the future, if the legacy build system stop's being supported.

I tried to contact some developers of the new build system in Twitter, to see if the new build system will support support -dry-run, but I'm not sure if it will. They proposed some alternative, but I'm not sure if it would work. https://twitter.com/4brunu/status/1059817210770845697 @lvsti Could you please take a look at the Twitter thread? What do you think of this?