arla on dual amd 64-bit

[Harald Barth]

>> KERNBUILDDIR when running bsd make on FreeBSD-Makefile.  I seem to be
>> able to get the directory from `uname -v | sed -e 's/.*://'`, but that
>> sounds a bit like a hack ...

> Don't try to do that.  Just let the admin supply the proper value.

I don't think that is good enough because this limits Arla on FreeBSD
to "admin skill level" persons. I think we should aim for more than
that.

Harald.