Add a benchmark for aarch64's __init_cpu_features_resolver()

[jroelofs]

No description provided.

[labrinea]

Thanks for writing these tests. Do they need adaptation for other operating systems?

[jroelofs]

Yes. There are some subtle differences in the signature of __init_cpu_features_resolver(), where on some platforms it takes a hwcap + __ifunc_arg_t*, and others it takes no arguments.

[labrinea]

Looks good, thanks! I'll write the equivalent linux tests at some point.