bug#47031: False positives for ‘-Wunbound-variable’ in 3.0.5

The new ‘unbound-variable’ warning in 3.0.5 has false positives, as in
this example:

--8<---------------cut here---------------start------------->8---
$ cat /tmp/unbound.scm
(use-modules (srfi srfi-35))

(condition (&message (message "oh no!"))
           (&serious))
$ guild compile -Wunbound-variable /tmp/unbound.scm
/tmp/unbound.scm:3:0: warning: possibly unbound variable `make-compound-condition'
wrote `/home/ludo/.cache/guile/ccache/3.0-LE-8-4.4/tmp/unbound.scm.go'
$ guild --version
guild (GNU Guile) 3.0.5
Copyright (C) 2021 Free Software Foundation, Inc.

License LGPLv3+: GNU LGPL 3 or later <http://gnu.org/licenses/lgpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
--8<---------------cut here---------------end--------------->8---

3.0.4 and earlier versions are fine.

Ludo’.