Stage 2 seems to be required after all

Author: camelid

CONTRIBUTING.md

@@ -148,11 +148,11 @@ cd rustc
 ./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.
+# Build a stage 2 rustc, and build the rustc libraries with that rustc.
 # This step can take 30 minutes or more.
-./x.py build --stage 1 compiler/rustc
+./x.py build --stage 2 compiler/rustc
 # If you change something, you can get a faster rebuild by doing
-./x.py build --keep-stage 0 --stage 1 compiler/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 stage1 build/x86_64-unknown-linux-gnu/stage1
 # Now cd to your Miri directory, then configure rustup