zsh: try to get daily script to die if build fails
zsh: try to get daily script to die if build fails

I just saw a build fail and we still tagged the build, so I made this
change. But in testing, it seems that the build exited with status 0...
Sigh. Keeping the change anyway because I like the explicitness.

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent