Up until this last version openzfs worked perfectly fine. 20200720 build fails with:
ld: error: unable to find library -ludev
libudev.so is provided by libudev-devd port in /usr/local/lib.
The build completes successfully when a symlink is created in /usr/lib, but I don't think it's the right thing to do. It seems that the port is not looking for the library in /usr/local/lib.
Thanks, I had run into this issue myself already and the fix has been merged upstream. I will be updating the port in the next few days.
Fixed by ports r544111