Most software development build environments are file system enlistments on disk, checked in/out from a central repository. You build and test from them, all day, every day. That's what a dev works on all the time. PVCS, Subversion, Perforce/SourceDepot (Microsoft uses), VSTS all act like this.
There's nothing to smuggle anywhere really; just keep whatever disk enlistments you already had on a home machine, external drive or laptop. You could already build whatever you liked, from cityofheroes.exe to the server executables and libraries.
I'd be shocked if there aren't quite a few folks who could build the client or server on a whim right now. But again, you will never know of them because its a no-no to admit to it.