Hi Guix,

Here's a patch to fix emacs-buttercup failing with native-comp, i.e. guix build emacs-buttercup --with-input=emacs-minimal=emacs.

Here is the link to the upstream issue: <https://github.com/jorgenschaefer/emacs-buttercup/issues/236>

In short, it should be fixed but the fix used a variable name in current git Emacs which is different in the current release. So this patch adds the older variable name with the same fix.

I checked that it lints and native-comp and regular both build. I'll wait for QA to check for any other breakages. And I welcome any input on the commit message/code comment here.

Thanks!
John