added it to the /usr/src/sys/i386/conf/MYKERNEL. It's the module for my sound chip.
device snd_es137x

started building (as described in 'kernelconfig-building.html' of FreeBSD handbook)
# cd /usr/src
# make buildkernel KERNCONF=MYKERNEL

The out:
............
............
............
............
In file included from /usr/src/sys/dev/sound/pcm/sound.h:93,
                 from /usr/src/sys/dev/sound/pci/es137x.c:51:
/usr/src/sys/dev/sound/pcm/channel.h:69:24: channel_if.h: No such file or directory
In file included from /usr/src/sys/dev/sound/pci/es137x.c:52:
/usr/src/sys/dev/sound/pcm/ac97.h:92:21: ac97_if.h: No such file or directory
/usr/src/sys/dev/sound/pci/es137x.c:60:22: mixer_if.h: No such file or directory
mkdep: compile failed
*** Error code 1

Stop in /usr/obj/usr/src/sys/MYKERNEL.
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.