message: don't assume a nightly toolchain is installed
diff: @@ -30,17 +30,17 @@ fi
  echo "$NEW_COMMIT" > rust-version
  # Check if we already are at that commit.
  -CUR_COMMIT=$(rustc +miri --version -v | egrep "^commit-hash: " | cut -d " " -f 2)
  +CUR_COMMIT=$(rustc +miri --version -v 2>/dev/null | egrep "^commit-hash: " | cut -d " " -f 2)
  if [[ "$CUR_COMMIT" == "$NEW_COMMIT" ]]; then
  echo "miri toolchain is already at commit $CUR_COMMIT."
  rustup override set miri
  exit 0
  fi
  -# Cleanup.
  -cargo +nightly clean # Use nightly cargo as miri toolchain might be broken.
  -rustup toolchain uninstall miri
  -
  # Install and setup new toolchain.
  +rustup toolchain uninstall miri
  rustup-toolchain-install-master -n miri -c rust-src -c rustc-dev -- "$NEW_COMMIT"
  rustup override set miri
  +
  +# Cleanup.
  +cargo clean
  