a.out: Stop building a.out/osf1 support on alpha and m68k

There has been repeated discussion on removing a.out support, the most
recent was[1].  Having read through a bunch of the discussion it looks
like no one has see any reason why we need to keep a.out support.

The m68k maintainer has even come out in favor of removing a.out
support[2].

At a practical level with only two rarely used architectures building
a.out support, it gets increasingly hard to test and to care about.
Which means the code will almost certainly bit-rot.

Let's see if anyone cares about a.out support on the last two
architectures that build it, by disabling the build of the support in
Kconfig.  If anyone cares, this can be easily reverted, and we can then
have a discussion about what it is going to take to support a.out
binaries in the long term.

[1] https://lkml.kernel.org/r/20220113160115.5375-1-bp@alien8.de
[2] https://lkml.kernel.org/r/CAMuHMdUbTNNr16YY1TFe=-uRLjg6yGzgw_RqtAFpyhnOMM5Pvw@mail.gmail.com



Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: linux-alpha@vger.kernel.org
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-m68k@lists.linux-m68k.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/87ilsmdhb5.fsf_-_@email.froward.int.ebiederm.org


Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/lkml/CAMuHMdVLyu6LNONJa1QcMGv__bWSCRvVq9haD7=fOm1k5O3Pnw@mail.gmail.com