Passing the tswapped structure to strace means that
our internal si_type is also gone, which then aborts
in print_siginfo.
Fixes: 4d6d8a05a0a ("linux-user: Move tswap_siginfo out of target code")
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>