Chicken and egg problem when building (third-party) kernel modules with <bsd.kmod.mk> -- how to solve?

[Lev Serebryakov]

Hello, Freebsd-current.

 It is good idea to set KERNBUILDDIR when build module. But to set it you
need to know ${.OBJDIR} from ${SYSDIR} and ${SYSDIR} is set in bsd.kmod.mk,
which should be included last (after defining KERNBUILDDIR).

 How this loop could be broken?

-- 
// Black Lion AKA Lev Serebryakov <lev at FreeBSD.org>