turbopack-cli: implement `turbopack build` (#5488)
Depends on #5487
This implements a basic version of `turbopack build`, only targeting
browser targets. In the future, we could accept a cli or configuration
option to target Node.
Test Plan: `cargo run -p turbopack-cli build` with a `src/index.js`
present and `cargo run -p turbopack-cli build src/entry.js` with
`src/entry.js` present.
