If you take a look at this irc log, and grep for "crap I nuked /usr/build/libtool", you'll find that someone has done exactly what I have done, trying to do exactly what I was trying to do.
The solution was simple,
ln -s /usr/bin/libtool /usr/build/libtool, but
usr/bin/libtool comes from the
libtool package, which wasn't installed on my system (?!). So I installed it, and symlinked it, no problem; but how the hack was there a
/usr/build/libtool anyway, without the
libtool package being installed? Where does it come from? I'd like to restore it.
And I know, I should have used
mv instead of
rm -rf, this was a good lesson.