Soundness issues in `raw-cpuid`

Undefined behavior in as_string() methods

VendorInfo::as_string(), SoCVendorBrand::as_string(),
and ExtendedFunctionInfo::processor_brand_string() construct byte slices
using std::slice::from_raw_parts(), with data coming from
#[repr(Rust)] structs. This is always undefined behavior.

See https://github.com/gz/rust-cpuid/issues/40.

This flaw has been fixed in v9.0.0, by making the relevant structs
#[repr(C)].

native_cpuid::cpuid_count() is unsound

native_cpuid::cpuid_count() exposes the unsafe __cpuid_count() intrinsic
from core::arch::x86 or core::arch::x86_64 as a safe function, and uses
it internally, without checking the
safety requirement:

> The CPU the program is currently running on supports the function being
> called.

CPUID is available in most, but not all, x86/x86_64 environments. The crate
compiles only on these architectures, so others are unaffected.

This issue is mitigated by the fact that affected programs are expected
to crash deterministically every time.

See https://github.com/gz/rust-cpuid/issues/41.

The flaw has been fixed in v9.0.0, by intentionally breaking compilation
when targeting SGX or 32-bit x86 without SSE. This covers all affected CPUs.