message: Update locally-built rustc instructions
diff: @@ -141,14 +141,17 @@ tracing) enabled.
  The setup for a local rustc works as follows:
  ```sh
  +# Clone the rust-lang/rust repo.
  git clone https://github.com/rust-lang/rust/ rustc
  cd rustc
  cp config.toml.example config.toml
  # Now edit `config.toml` and set `debug-assertions = true`.
  -# This step can take 30 minutes and more.
  -./x.py build src/rustc
  +
  +# Build a stage 2 rustc.
  +# This step can take 30 minutes or more.
  +./x.py build --stage 2 compiler/rustc
  # If you change something, you can get a faster rebuild by doing
  -./x.py --keep-stage 0 build src/rustc
  +./x.py build --keep-stage 0 --stage 2 compiler/rustc
  # You may have to change the architecture in the next command
  rustup toolchain link custom build/x86_64-unknown-linux-gnu/stage2
  # Now cd to your Miri directory, then configure rustup
  