Use no-op impl on miri

[bjorn3]

Stacker currently doesn't work on miri at all.

[nagisa]

yeah I don't see any reason why we shouldn't -- it isn't like miri has a weird platform-defined stack size anyway, does it? Is #[cfg(miri)] sufficient for this?

[bjorn3]

it isn't like miri has a weird platform-defined stack size anyway, does it?

I don't think so. And even if it does, miri doesn't provide any way to muck around with the stack like stacker needs to.

Is #[cfg(miri)] sufficient for this?

Should be.