bug#38600: Unbound variable for some package --show invocations.

[Jacob MacDonald]

Noticed the problem with cl-slime-swank, but seems to happen with a
variety of packages including sbcl-cl-uglify-js itself. I checked
javascript.scm, which does import lisp-xyz; Haven't done any deeper
debugging to discover possible causes.

Backtrace follows.

$ guix package --show=sbcl-cl-uglify-js
Backtrace:
In ice-9/boot-9.scm:
   222:29 19 (map1 (((gnu packages gettext)) ((gnu packages #)) (#) …))
   222:29 18 (map1 (((gnu packages ghostscript)) ((gnu packages …)) …))
   222:29 17 (map1 (((gnu packages gl)) ((gnu packages glib)) ((…)) …))
   222:29 16 (map1 (((gnu packages glib)) ((gnu packages gnome)) # …))
   222:29 15 (map1 (((gnu packages gnome)) ((gnu packages gnupg)) # …))
   222:29 14 (map1 (((gnu packages gnupg)) ((gnu packages #)) ((…)) …))
   222:29 13 (map1 (((gnu packages gstreamer)) ((gnu packages #)) # …))
   222:29 12 (map1 (((gnu packages gtk)) ((gnu packages image)) (#) …))
   222:29 11 (map1 (((gnu packages image)) ((gnu packages #)) ((…)) …))
   222:29 10 (map1 (((gnu packages imagemagick)) ((gnu packages …)) …))
   222:17  9 (map1 (((gnu packages javascript)) ((gnu packages #)) …))
  2800:17  8 (resolve-interface (gnu packages javascript) #:select _ …)
In ice-9/threads.scm:
    390:8  7 (_ _)
In ice-9/boot-9.scm:
  2726:13  6 (_)
In ice-9/threads.scm:
    390:8  5 (_ _)
In ice-9/boot-9.scm:
  2994:20  4 (_)
   2312:4  3 (save-module-excursion #<procedure 7fbf1f28b330 at ice-…>)
  3014:26  2 (_)
In unknown file:
           1 (primitive-load-path "gnu/packages/javascript" #<proced…>)
In gnu/packages/javascript.scm:
   460:10  0 (_)

gnu/packages/javascript.scm:460:10: error: sbcl-cl-uglify-js: unbound variable