bug#56540: ‘home-bash-service-type’ doesn’t quote environment variables

[Ludovic Courtès]

Similar to <https://issues.guix.gnu.org/54469>, ‘home-bash-service-type’
doesn’t quote environment variables.  For example, if you add this
service:

--8<---------------cut here---------------start------------->8---
(define bash-fancy-prompt-service
  (simple-service 'bash-fancy-prompt
                  home-bash-service-type
                  (home-bash-extension
                   (environment-variables
                    '(("PS1" . "\\u@\\h \\wλ "))))))
--8<---------------cut here---------------end--------------->8---

… you end up with invalid shell code:

--8<---------------cut here---------------start------------->8---
$ tail -1 $(guix build 
/gnu/store/maz98q1skyc7md2vknkg8ima3y2bq5yr-bash_profile.drv)
export PS1=\u@\h \wλ 
--8<---------------cut here---------------end--------------->8---

Ludo’.