[racket] Building Racket 5.2.1 on 64-bit Ubuntu?

I'm trying to install Racket 5.2.1 on my shiny new Ubuntu box, and am
encountering some strangeness when doing 'make install'.  It appears
to get stuck doing the documentation build for macro-debugger.

###############################
...
raco setup: 2 making: lang/private
raco setup: 2 making: launcher
raco setup: 2 making: launcher/tests
raco setup: 2 making: lazy
raco setup: 2 making: lazy/lang
raco setup: 2 making: macro-debugger
###############################

The CPU's pegged at 100% at this point, but I see no progress
otherwise.  What else can I do to help debug this?