$ vm.sh run_root 'cd /tmp/df4606 && make'   (stock X86_64_GENERIC kernel tree, /usr/src via with-src snapshot)
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/tmp/df4606/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 df4606.c
cc -Wl,--build-id=sha1 -nostdlib -Wl,--hash-style=sysv   -r -Wl,-d -o df4606.ko df4606.o
-rw-r--r-- 1 root wheel 5720 (run 2 build) / 6688 (run 3 build, with sysctl probe) df4606.ko
BUILD_OK (three successful builds across the three reset/with-src cycles)