softmmu: pass the main loop status to gdb "Wxx" packet

gdb_exit function aims to close gdb sessions and sends the exit code of
the current execution. It's being called by qemu_cleanup once the main
loop is over.
Until now, the exit code sent was always 0. Now that hardware can
shutdown this main loop with custom exit codes, these codes must be
transfered to gdb as well.

Signed-off-by: Clément Chigot <chigot@adacore.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20231003071427.188697-3-chigot@adacore.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

system/main.c

@@ -35,7 +35,7 @@ int qemu_default_main(void)
     int status;
 
     status = qemu_main_loop();
-    qemu_cleanup();
+    qemu_cleanup(status);
 
     return status;
 }