Bug#723977: missing symlink in /usr/share/common-lisp/systems

[Diogo F. S. Ramos]

> HOME=/tmp sbcl --noinform --non-interactive --eval '(require :asdf)'
> --eval '(format t "~A~%" (asdf:system-source-directory :cl-ppcre))'
> /usr/share/common-lisp/source/cl-ppcre/
>
> (The HOME=/tmp is so it won't use my personal configuration files)
>
> I blame your misconfiguration.
>
> If you don't use XDG_DATA_DIRS, do you have something in your configuration
> that uses :ignore-inherited-configuration
> then goes on to register /usr/share/common-lisp/systems ?

I used your exact incantation but I didn't get the same result, even
though I have `cl-ppcre' installed at
`/usr/share/common-lisp/source/cl-ppcre/'.

  Unhandled ASDF/FIND-SYSTEM:MISSING-COMPONENT in thread #<SB-THREAD:THREAD
                                                         "main thread" RUNNING
                                                          {1002ADB373}>:
  Component "cl-ppcre" not found

I can have the same result if I prepend it with
`XDG_DATA_DIRS=/usr/share/':

  XDG_DATA_DIRS=/usr/share/ HOME=/tmp sbcl --noinform --non-interactive
  --eval '(require :asdf)' --eval '(format t "~A~%"
  (asdf:system-source-directory :cl-ppcre))'
  /usr/share/common-lisp/source/cl-ppcre/