message: readme: be more explicit about the toolchain
diff: @@ -81,8 +81,11 @@ rustup +nightly component add miri
  If `rustup` says the `miri` component is unavailable, that's because not all
  nightly releases come with all tools. Check out
  [this website](https://rust-lang.github.io/rustup-components-history) to
  -determine a nightly version that comes with Miri and install that using
  -`rustup toolchain install nightly-YYYY-MM-DD`.
  +determine a nightly version that comes with Miri and install that using `rustup
  +toolchain install nightly-YYYY-MM-DD`. Either way, all of the following commands
  +assume the right toolchain is pinned via `rustup override set nightly` or
  +`rustup override set nightly-YYYY-MM-DD`. (Alternatively, use `cargo
  ++nightly`/`cargo +nightly-YYYY-MM-DD` for each of the following commands.)
  Now you can run your project in Miri:
  