make: Suppress a new warning

In Emacs 30 the advertised signature of `derived-mode-p' was changed
from (&rest modes) to (modes).  The old calling convention is still
supported, and we have no choice but to keep using that for a few
more releases.

borg.mk

@@ -32,6 +32,7 @@ EMACS_EXTRA ?=
 
 SILENCIO  = --load subr-x
 SILENCIO += --eval "(setq byte-compile-warnings '(not docstrings))"
+SILENCIO += --eval "(remhash (indirect-function 'derived-mode-p) advertised-signature-table))"
 SILENCIO += --eval "(fset 'original-message (symbol-function 'message))"
 SILENCIO += --eval "(fset 'message\
 (lambda (format &rest args)\