fix zsh eating output without new line ending

[cuichenli]

caught the issue described in here https://github.com/NixOS/nixpkgs/issues/30121 and feeling it is worth to patch a fix here.

basically the issues is that when you run a command with output missing the new line ending, it will not be displayed.

root@nixos> echo -n "abc\ndef"
abc

something like this ☝️