We previously weren't generating source maps when running `babel-build` in `dev`.
This led to a pretty painful debugging experience for `keyserver` in VSCode/WebStorm/etc. If the developer wanted to set breakpoints they'd need to
1. Navigate out of the `src` file to the corresponding file in `dist` (tedious/context switch.etc)
2. Set breakpoints in transpiled output which often looked pretty different from source
In addition, the developer would need to keep hopping between the files because `dist` got rewritten on changes to `src` which meant the developer couldn't just iterate within `dist`.
This diff adds the `--source-maps` flag to `babel-build` for `dev` which enables a much smoother debugging experience. Breakpoints can be set directly in source and iteration can happen in realtime.
I should have investigated this much much earlier...