message: Add alternative for how to install if rustup fails
  As is the case now:
diff: @@ -88,9 +88,19 @@ fn does_not_work_on_miri() {
  ### Common Problems
  -When using the above instructions, you may encounter a number of confusing compiler
  +When using the above instructions, you may encounter a number of confusing
  errors.
  +#### "component 'miri' for target '\<target\>' is unavailable for download for channel 'nightly'"
  +
  +The latest nightly may have broken Miri. If [this is the case][rust-toolstate], instead try to install Miri the old way with
  +
  +```sh
  +cargo +nightly install --force --git https://github.com/rust-lang/miri miri
  +```
  +
  +[rust-toolstate]:
  +
  #### "found possibly newer version of crate `std` which `<dependency>` depends on"
  Your build directory may contain artifacts from an earlier build that have/have
  