because my cowbuilder bind mounts my build area so that its path looksI just checked and it builds fine for me, but I suspect that it's
the same to the bits of the build that run before entering the chroot to
those after entering that chroot. That is, /path/to/foo is accessible
to both because /path exists both inside and outside the chroot.
One thing you might try is running a shell the in chroot using --login,
doing an apt-get build-dep $foo, and then initiating the build from
within the chroot with debuild or similar. I do this frequently enough
that I have a bash function that does something like this:
sudo cowbuilder --bindmounts /buildarea --bindmounts $HOME --login
--basepath=/var/cache/pbuilder/base-${chroot}.cow $@
(Note: bind-mounting $HOME is potentially dangerous - anything you
delete/modify is changed outside of the chroot as well.)