[racket] Build documentation with more than one job

At Thu, 07 Mar 2013 01:21:13 +0100, Juan Francisco Cantero Hurtado wrote:
> On 03/06/13 22:30, Matthew Flatt wrote:
> > Meanwhile, beware that `-j' isn't useful without support for places.
> > (Probably `raco setup' should issue a warning in that case..)
> 
> OK. I was just testing if "-j N" reduces the build time. Apparently it 
> uses my two cores.

You're right. I forgot that `raco setup' uses multiple OS processes if
Racket is built without parallel places. So, `-j' can be useful after
all.

I've finally fixed the bug (now in the git repo, to be included in the
next release).