=== netgraph7 core module build (representative) ===
$ make -C /usr/src/sys/netgraph7/netgraph
cc ... -c /usr/src/sys/netgraph7/netgraph/ng_base.c
cc ... -c /usr/src/sys/netgraph7/netgraph/ng_parse.c
cc -Wl,--build-id=sha1 -nostdlib -Wl,--hash-style=sysv -r -Wl,-d -o netgraph.ko ng_base.o ng_parse.o

=== ng_socket7 module build ===
cc ... -c /usr/src/sys/netgraph7/socket/ng_socket.c
cc -Wl,--build-id=sha1 ... -o ng_socket.ko ng_socket.o

=== ng_split module build (KCFLAGS=-DINVARIANTS, so KKASSERT live) ===
$ cd /usr/src/sys/netgraph7/split  # hand-authored Makefile (KMOD=ng_split SRCS=ng_split.c KCFLAGS=-DINVARIANTS)
cc -O2 -pipe -DINVARIANTS -D_KERNEL ... -c /usr/src/sys/netgraph7/split/ng_split.c
cc -Wl,--build-id=sha1 ... -o ng_split.ko ng_split.o
[+] ng_split.ko has INVARIANTS assertion compiled in   # sanity: KKASSERT string present

=== injector build ===
$ cc -O2 -Wall -o inject inject.c -lnetgraph   # libnetgraph7 (NG_VERSION=8)
BUILD_OK