When a kernel is built without KDB and DDB, it fails with:
--- kernel.full --- linking kernel.full ld: error: undefined symbol: db_ctf_lookup_typename >>> referenced by kern_ctf.c:329 (/usr/src/sys/kern/kern_ctf.c:329) >>> link_elf_obj.o:(link_elf_ctf_lookup_typename) >>> referenced by kern_ctf.c:329 (/usr/src/sys/kern/kern_ctf.c:329) >>> link_elf.o:(link_elf_ctf_lookup_typename) *** [kernel.full] Error code 1
