AVX/AVX2 not correcly detected in user mode

Hi,

Thanks for supporting AVX/AVX2 in 7.2. However it seems that canonical detection of feature does not work in user mode, this fail qemu-x86_64 -cpu qemu64,+avx ./a.out

include <sys/resource.h>
#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>

#include <argp.h>

#include <sys/auxv.h>

#if defined(__x86_64__) || defined(__i386__)
#include <sys/platform/x86.h>
#endif

const char *argp_program_version = "test-x86-64-v3 version 17";
static char doc[] = "doc";
static struct argp argp = { 0, 0, 0, doc };


const struct rlimit nocore = { 0, 0 };

/* emulate kill by signal */
void
termination_handler (int signum)
{
    _exit(128+signum);
}

int main(int argc,char **argv)
{
    /* no core */
    (void) setrlimit(RLIMIT_CORE, &nocore);
    /* return instead */
    struct sigaction new_action;
    new_action.sa_handler = termination_handler;
    (void) sigemptyset (&new_action.sa_mask);
    new_action.sa_flags = 0;
    (void) sigaction (SIGILL, &new_action, NULL);
    (void) sigaction (SIGBUS, &new_action, NULL);
    (void) sigaction (SIGSEGV, &new_action, NULL);
    argp_parse (&argp, argc, argv, 0, 0, 0);
    /* now test */
    return !(
     __builtin_cpu_supports("avx")
 );;
    return 0;
}