linux-user/elfload: check PR_GET_DUMPABLE before creating coredump

linux-user/elfload: check PR_GET_DUMPABLE before creating coredump

A process can opt-out of coredump creation by calling
prctl(PR_SET_DUMPABLE, 0).
linux-user passes this call from the guest through to the
operating system.
From there it can be read back again to avoid creating coredumps from
qemu-user itself if the guest chose so.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
Message-Id: <20240120-qemu-user-dumpable-v3-2-6aa410c933f1@t-8ch.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>