test/statx: be safe and check if __NR_statx is there
test/statx: be safe and check if __NR_statx is there

Probably don't need this, but it's right before release and I'd hate
for a test to cause compilation failure.

Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

axboe/liburing,axboe/liburing,axboe/liburing