Comment 2 for bug 2047156

A big +1 to this idea generally.

Would it be possible/feasible to mark some routes such that they don't get built for release? My first thought was the --configuration parameter to `ng build`, but since there are (AIUI) some subtle behavioral differences between dev and prod build modes (certain error checking/reporting only happens in one or the other mode, for instance) we probably (maybe especially?) want the sandbox and style-guide to be available and testable in both.