linux-user: Move TARGET_SA_RESTORER out of generic/signal.h

linux-user: Move TARGET_SA_RESTORER out of generic/signal.h

SA_RESTORER and the associated sa_restorer field of struct sigaction are
an obsolete feature, not expected to be used by future architectures.
They are also absent on RISC-V, LoongArch, Hexagon and OpenRISC, but
defined due to their use of generic/signal.h.  This leads to corrupted
data and out-of-bounds accesses.

Move the definition of TARGET_SA_RESTORER out of generic/signal.h into the
target_signal.h files that need it.  Note that m68k has the sa_restorer
field, but does not use it and does not define SA_RESTORER.

Reported-by: Thomas Weißschuh <thomas@t-8ch.de>
Signed-off-by: Andreas Schwab <schwab@suse.de>
Reviewed-by: Thomas Weißschuh <thomas@t-8ch.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <mvmed060xc9.fsf@suse.de>