kunit/fortify: Do not spam logs with fortify WARNs

When running KUnit fortify tests, we're already doing precise tracking
of which warnings are getting hit. Don't fill the logs with WARNs unless
we've been explicitly built with DEBUG enabled.

Link: https://lore.kernel.org/r/20240429194342.2421639-2-keescook@chromium.org


Signed-off-by: Kees Cook <keescook@chromium.org>