bug#40550: zsh: sudo is not setuid

["Alexandru-Sergiu Marton" <brown121407@posteo.ro>]

Hi,

I changed my default shell to zsh with the following line added to
my user-account record in my config.scm:

(shell #~(string-append #$zsh "/bin/zsh"))

After reconfiguring the system and rebooting, when I try to run sudo or
su (I guess this problem appears for every thing in %setuid-programs), I
get a message saying it isn't actually a setuid program.

I'm writing this from a reconfigured system started at the same point as
the zsh one started, but with bash. Here I don't have that problem --
setuid programs work as expected.

Steps to reproduce:
- $ guix pull
- Change the default shell to zsh in your config.scm, as presented
  above.
- $ sudo guix system reconfigure config.scm
- Reboot.
- Try to run sudo or su. It should give you an error.

Cheers,
Sergiu