I posted up some build details a while back, these might (or might not) help you.
You can build R&Dt by following the Master process, but cloning the location you’re already using rather than the mainstream git location. You can have various independent builds of dt/R&Dt if you wish.
Are you sure you’ve built R&Dt? Was that your intention? I think by using the 3.8.1 tag you’ve built mainstream dt of that version. Or am I misunderstanding something? Have another look at the README in Aurelien’s github.