=== feeder (userland, guest) ===
$ cc -O2 -Wall -o pfilrace_feeder pfilrace_feeder.c
(no diagnostics)

=== prhook.ko (KLD, guest) ===
$ cd prhook && make -m /usr/src/share/mk
creating machine/ forwarding headers (forwarder_x86_64/...)
cc -O2 -pipe -D_KERNEL -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes
   -Wmissing-prototypes -Wpointer-arith -Wcast-qual -Wold-style-definition
   -Wmissing-include-dirs -Wno-pointer-sign -Winit-self -Wundef
   -Wno-unused-but-set-variable -std=gnu11 -Werror -DKLD_MODULE -nostdinc -I.
   -Idragonfly -I... -Wold-style-declaration -fno-common -ffreestanding
   -fno-stack-protector -fno-strict-aliasing -fno-strict-overflow
   -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -mcmodel=kernel
   -mno-red-zone -mno-mmx -mno-sse -msoft-float -mno-fp-ret-in-387
   -mindirect-branch=thunk-inline -c prhook.c
cc -Wl,--build-id=sha1 -nostdlib -Wl,--hash-style=sysv -r -Wl,-d -o prhook.ko prhook.o
-rw-r--r-- 1 root wheel 9480 Sep 13 01:37 prhook.ko

=== PRNOINV kernel (in-guest nativekernel) ===
$ sed -e "s/^options 	INVARIANTS/#options 	INVARIANTS/" -e "s/^makeoptions	DEBUG=-g/#&/" \
    /usr/src/sys/config/X86_64_GENERIC > /usr/src/sys/config/PRNOINV
$ cd /usr/src && make -j 6 nativekernel KERNCONF=PRNOINV
>>> Kernel build for PRNOINV completed  (kernel.stripped 15010320 bytes)
$ cp /usr/obj/usr/src/sys/PRNOINV/kernel.stripped /boot/kernel/kernel && reboot