Add GraalVM 20.2.0

case $(uname -s) in

Linux)

  install_package "truffleruby+graalvm-20.2.0" "https://github.com/graalvm/graalvm-ce-builds/releases/download/vm-20.2.0/graalvm-ce-java8-linux-amd64-20.2.0.tar.gz#60951c774c708caeebd1fa3886c05aa1260d81c7595ede0c9c3e689be7fcc4e8" truffleruby_graalvm

  ;;

Darwin)

  use_homebrew_openssl

  install_package "truffleruby+graalvm-20.2.0" "https://github.com/graalvm/graalvm-ce-builds/releases/download/vm-20.2.0/graalvm-ce-java8-darwin-amd64-20.2.0.tar.gz#a1f524788354cfd2434566f0de972372f4a7743919bae49a9d508f2080385e7b" truffleruby_graalvm

  ;;

*)

  colorize 1 "Unsupported operating system: $(uname -s)"

  return 1

  ;;

esac