message: Improve contributing instructions
  Fix incorrect comment
  Recommend `x.py setup` over manually editing config.toml
  Link to rustc-dev-guide
diff: @@ -144,8 +144,9 @@ The setup for a local rustc works as follows:
  # 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`.
  +# Create a config.toml with defaults for working on miri.
  +./x.py setup compiler
  + # Now edit `config.toml` and under `[rust]` set `debug-assertions = true`.
  # Build a stage 1 rustc, and build the rustc libraries with that rustc.
  # This step can take 30 minutes or more.
  @@ -158,5 +159,8 @@ rustup toolchain link stage1 build/x86_64-unknown-linux-gnu/stage1
  rustup override set stage1
  ```
  +For more information about building and configuring a local compiler,
  +see <https://rustc-dev-guide.rust-lang.org/building/how-to-build-and-run.html>.
  +
  With this, you should now have a working development setup! See
  [above](#building-and-testing-miri) for how to proceed working on Miri.
  