$ cd /tmp/df2728 && make obj && make
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/usr/obj/tmp/df2728/forwarder_x86_64/include -Idragonfly/../include
    -I/usr/include -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 /tmp/df2728/df2728.c
cc -Wl,--build-id=sha1 -nostdlib -Wl,--hash-style=sysv   -r -Wl,-d -o df2728.ko df2728.o
(result: /usr/obj/tmp/df2728/df2728.ko, exit 0, zero warnings)