[tlbuild] build/test errors with seetex in chroot

[Karl Berry]

    cat playsel.dvi | ./dvibook -s4 >playbook.dvi \
    ...
    where I get as output (in playbook2)
            ...seetexk/.libs/lt-dvibook: can't seek file

Sounds like reading from a pipe is failing in the cow environment.
I suspect that is the seek (into the dvi file) that is failing, although
of course the program should be reporting explicitly.  Sigh.

If that wild guess is right, there's an obvious workaround:
  ./dvibook -s4 <playsel.dvi >playbook.dvi \
to read directly from the file instead of a pipe ... -k