buildenv target

[John-Mark Gurney]

Does anyone object to adding a buildenv target to our Makefile, so that
when crossbuilding you can get the tools setup in a shell.  Useful for
doing crossbuild testing w/ a cross-built world eaiser.

http://people.freebsd.org/~jmg/buildenv.patch

so:
bash-2.05b$ which config
/usr/sbin/config
bash-2.05b$ make buildenv TARGET_ARCH=arm
Entering world for arm:arm
bash-2.05b$ which config
/usr/obj/arm/usr/home/jmg/arm/src/i386/legacy/usr/sbin/config

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."