Build failure when compiling for x86

[mox692]

It seems that we would get an error when we try to build the fastant for x86 (for example i686-unknown-linux-gnu).

$ cargo build --target i686-unknown-linux-gnu

error[E0432]: unresolved import `core::arch::x86_64`
   --> src/tsc_now.rs:131:25
    |
131 |         use core::arch::x86_64::__cpuid;
    |                         ^^^^^^ could not find `x86_64` in `arch`

Is this expected or something we want to fix?

[tisonkun]

Closed by #6