Add simple Builder for the hello_world recipe

This is from LUCI's onboarding docs

Change-Id: Ifb373f87be6d7d378a8c9785af5d9d24915282d5
3 files changed
tree: f36deb09fac5d695ac450739561a1e9ff633c527
  1. generated/
  2. infra/
  3. recipes/
  4. .gitignore
  5. main.star