bug#57119: Warning level 0 still yields warnings

[Jean Abou Samra]

For example:

$ cat cased.scm
(case 5
  ((5 5) 5))
$ guild3.0 compile -W0 cased.scm
cased.scm:2:3: warning: duplicate datum 5 in clause ((5 5) 5) of case 
expression (case 5 ((5 5) 5))
wrote `/[...]/cased.scm.go'

The documentation says that passing -W0 suppresses all warnings.
The above shows that this is not the case, at least not for
all warnings.

This is with Guile 3.0.7.