[racket-dev] building from a git checkout into a separate BUILD directory

I am building from a (relatively recent) git checkout.  I have been
using the in-place make target which installs in ./racket, but I'd like
to have everything built and installed in a separate BUILD directory.
My motivations are to have a single directory to rm -r when I want to
start over and secondly to have a single directory to exclude from my
nightly backups.

I can get the base built with:

  mkdir BUILD
  cd BUILD
  ../racket/src/configure --prefix=$PWD
  make && make install

but then I need to deal with packages.  I was able to hack the
link-all.rkt to kinda work but the subsequent raco setup didn't seem to
do anything significant.  I'm pretty sure my hack was the wrong approach
anyway, so I won't detail my steps with that.

Is there an easy way to do what I want?

Thanks for any help.

David