kbuild: Port silent mode detection to future gnu make.

Port silent mode detection to the future (post make-4.4) versions of gnu make.

Makefile contains the following piece of make code to detect if option -s is
specified on the command line.

ifneq ($(findstring s,$(filter-out --%,$(MAKEFLAGS))),)

This code is executed by make at parse time and assumes that MAKEFLAGS
does not contain command line variable definitions.
Currently if the user defines a=s on the command line, then at build only
time MAKEFLAGS contains " -- a=s".
However, starting with commit dc2d963989b96161472b2cd38cef5d1f4851ea34
MAKEFLAGS contains command line definitions at both parse time and
build time.

This '-s' detection code then confuses a command line variable
definition which contains letter 's' with option -s.

$ # old make
$ make net/wireless/ocb.o a=s
  CALL    scripts/checksyscalls.sh
  DESCEND objtool
$ # this a new make which defines makeflags at parse time
$ ~/src/gmake/make/l64/make net/wireless/ocb.o a=s
$

We can see here that the letter 's' from 'a=s' was confused with -s.

This patch checks for presence of -s using a method recommended by the
make manual here
https://www.gnu.org/software/make/manual/make.html#Testing-Flags.

Link: https://lists.gnu.org/archive/html/bug-make/2022-11/msg00190.html


Reported-by: Jan Palus <jpalus+gnu@fastmail.com>
Signed-off-by: Dmitry Goncharov <dgoncharov@users.sf.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>