story: agd installable by npm

[turadg]

What is the Problem Being Solved?

Some CLI commands shell out to agd. While users can npm install agoric the only way currently to get agd is to build it. This necessitates checking out agoric-sdk and having Go tools.

Description of the Design

We currently have @agoric/cosmos (under golang/, not packages/) which provides a build configuration for agd. However, installing the package doesn't build agd, so that JS developers testing their smart contracts can do so without building agd.

Create a package that has prebuilds of agd for supported platforms (or include it in the agoric package).

These should help:
https://github.com/goreleaser/goreleaser
https://github.com/sanathkr/go-npm

Security Considerations

Scaling Considerations

Test Plan