message: fix rustup-toolchain without arguments
diff: @@ -30,7 +30,7 @@ else
  NEW_COMMIT="$1"
  fi
  echo "$NEW_COMMIT" > rust-version
  -shift
  +shift || true # don't fail if shifting fails
  # Check if we already are at that commit.
  CUR_COMMIT=$(rustc +miri --version -v 2>/dev/null | egrep "^commit-hash: " | cut -d " " -f 2)
  