how to get one OBJDIR per kernel

[[LoN]Kamikaze]

I have several systems which all use the same /usr/obj over NFS.
In the make.conf of those systems WRKDIRPREFIX is set to /usr/obj/${HOST},
which keeps machines from messing with each other while they build ports.

Those machines have their own kernel configurations, which reside in
/root/kernels/ and are linked from /usr/src/sys/ARCH/conf . I also have
the following in my make.conf .

# Load specific configuration for the kernel.
.if exists(/root/kernels/${KERNCONF}.mk)
.include "/root/kernels/${KERNCONF}.mk"
.endif

This way I can have settings for a different world per kernel as well.
I.e. with NO_PROFILE set for kernels without debugging. The trouble is
that different kernels still clash in the same OBJDIR. I would like to
have something like MAKEOBJDIRPREFIX=/usr/obj/${KERNCONF} , the trouble
being that it cannot be set in make.conf .
Is there a way around this restriction?