shelltest.od: detect some weird zsh problems.
shelltest.od: detect some weird zsh problems.

This seems to only affect old zsh on MacOS.  But we want to catch it
anyway, because it caused t/351-deps-forget to fail in a weird way on
that version of zsh.

Shells really suck.

apenwarr/redo,apenwarr/redo,apenwarr/redo,apenwarr/redo