[racket-dev] Parallel Build of Collects

raco setup -u will build collects in parallel, using all the cores your 
machine has.
rack setup -u -j X ie (-j 2) can be used to throttle parallel build to 
only use X cores.

Parallel build is currently done by spawning worker processes and 
communicating over pipes.
Building scribble documentation is still serial, I'm working to 
parallelize that as well.

Kevin