Open-source Dracon build_defs for please.build

[VJftw]

Enhancement

Current behaviour

We do not open-source our dracon build_defs for plz so external users cannot use dracon w/ plz the same way that we do.

Disadvantages of current behaviour

• Separation of community and Thought Machine usage, leads to increased maintenance overhead

New behaviour

Open-sourced build_defs which we re-use internally at Thought Machine.

Advantages of new behaviour

• Transparent usage of dracon