Some of the larger application sets on DragonFly have had trouble building, and inconsistent problems with that build. i.e. rust would fail, but in different parts of the build process, every time. It looks to be a problem with signal interaction, and there’s now much safer ways to do that on DragonFly.
That is going to require a full buildworld/buildkernel if you are on DragonFly-master, 5.7. Release/5.6 users are unaffected.