how about of erroring here add something like:

    gnu_missing=()
    for gnu_util in "${gnu_utils[@]}"
    do
      if
        [[ -x $gnu_tools_path/$gnu_prefix$gnu_util ]]
      then
        eval "__rvm_$gnu_util() { $gnu_tools_path/$gnu_prefix$gnu_util \"\$@\" || return \$?; }"
      else
        gnu_missing+=( $gnu_util )
      fi
    done
    if
      (( ${#gnu_missing[@]} ))
    then
      rvm_error "ERROR: Missing GNU tools: ${gnu_missing[@]}. Make sure they are installed in '$gnu_tools_path/' before using RVM!"
      exit 1
    fi
    unset gnu_missing