Add new --disallow-system-packages flag to `generate-github-actions`
Add new --disallow-system-packages flag to `generate-github-actions`

Summary:
- Make OpenR build all deps from source until we remove fbzmq as a dep
- Allow a project to move it's Open Source CI forward to an alternative version of ubuntu via a new `--ubuntu-version` parameter

Reviewed By: wez

Differential Revision: D22768987

fbshipit-source-id: 07205efbd0c87a702638cf30b84a2850d064fa8e

ReactiveSocket/reactivesocket-cpp,ReactiveSocket/reactivesocket-cpp,rsocket/rsocket-cpp,ReactiveSocket/reactivesocket-cpp,rsocket/rsocket-cpp,rsocket/rsocket-cpp,rsocket/rsocket-cpp