Rollup merge of #74241 - RalfJung:miri, r=RalfJung
Rollup merge of #74241 - RalfJung:miri, r=RalfJung

update miri

This incorporates https://github.com/rust-lang/miri/pull/1474. [Last time](https://github.com/rust-lang/rust/pull/74146) that change caused trouble but I fixed xargo since then and [now it should work](https://github.com/rust-lang/rust/pull/74146#issuecomment-657051446).

Cc @rust-lang/miri r? @ghost

graydon/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust