I haven't even figured out exactly what it's for.  Actually, that's not quite
   true:  I have a vague belief that the idea is that I can have a read-only
   /usr/src, NFS-mounted to hell and back, and everyone uses /home/obj for
   builds, and it All Just Works.
   
   Is this roughly correct?


i have /usr/src NFS or nullfs mounted read-only.  i set MAKEOBJDIRPREFIX
to ``/var/obj.${MACHINE}''.  this means that when i do a sparc build,
objects end up in /var/obj.sparc/$cwd, etc.  MAKEOBJDIRPREFIX is only
settable in the environment as it is handled *before* the makefile is
read.  there is one caveat:  you'll have to run "make obj" before hand
or "make cleandir" will barf somewhere...