See attached build log.
(Please do not complain about the need for looking at the build log until you can provide an easy way to open bugs with the correct data picked out of a tinderbox log. Thanks.)
Created attachment 248138 [details]
Fixed in -r1. I would have bumped to 5.0.2 but then saw the notice that everything had moved to <http://opensource.iis.se/trac/bbk>, which in turn seems to have been abandoned a couple of years ago.