Proposal: add none implement for Pretouch under arm arch.

[xiekeyi98]

Now functions like Pretouch only compile under amd64.
https://github.com/bytedance/sonic/blob/main/sonic.go#L1

How about using the conditional compilation to provide a none implement under arm64?
(I think it will be helpful for some users to develop their code which not use conditional compilation to use Pretouch feature under Apple M1.

It will be like

build !amd64


// None Implement for !amd64
func Pretouch(vt reflect.Type, opts ...option.CompileOption) error {
	 return nil.
}

[AsterDY]

Thanks for the feedback. We will add it on our next version

[xiekeyi98]

If you accept this change, I was wondering would you mind let me have a try？