I want to create a build daemon backend so that zb can run without a Nix installation. I'm thinking the protocol should be JSON-RPC-ish for simplicity. I like the LSP framing format, since that would also permit streaming NAR imports as a separate content type.

• Finish enough of build daemon to run stage0 #13
• Resolve derivations with dependencies #14
• Check for conflicting outputs in closure #26
• Finish enough of build daemon to run live-bootstrap #25