Misplaced "type": "module"

[michaelfig]

When building SwingSet:

> @agoric/[email protected] build-kernel /Users/michael/agoric/agoric-sdk/packages/SwingSet
> node -r esm scripts/build-kernel.js

(node:76257) Warning: require() of ES modules is not supported.
require() of /Users/michael/agoric/agoric-sdk/packages/bundle-source/src/index.js from /Users/michael/agoric/agoric-sdk/packages/SwingSet/scripts/build-kernel.js is an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which defines all .js files in that package scope as ES modules.
Instead rename index.js to end in .cjs, change the requiring code to use import(), or remove "type": "module" from /Users/michael/agoric/agoric-sdk/packages/bundle-source/package.json.