When the kernel is built with INVARIANTS we also need to build ZFS with INVARIANTS. Additionally, the knob for this has been broken out from WITH_DEBUG=true to WITH_INVARIANTS=true in the OpenZFS build system. We add an INVARIANTS option to the port for this, and enable the DEBUG and INVARIANTS options by default on 13-CURRENT to ensure that a default configuration builds openzfs-kmod with the correct options. Users building their 13-CURRENT kernel without INVARIANTS will need to disable the INVARIANTS option in the port manually. I'm not aware of a better way to implement this decision at the moment.