Most likely you have leftover .o files (containing the wrong architectures) from previous builds.
Yup, something like that. Tried again from scratch and it worked :) at least the same guy on the facebook group said it works now! I also didn't get weird or alarming warnings. Deken also packages it correctly without complaining (but I can't upload it yet).
As for the 'spctl --master-disable' command, I hear it disables Gatekeeper, the thing that keeps unsigned or whatever apps from running. I wonder if I can do anything about it, huh?
Thanks!