function getPolyfillDependencies() {
  /** @type {Map<string, string[]>} */
  const polyfillDependencies = new Map();

  for (const {name} of getCoreJsPolyfillData()) {
    const folder = name.replace(/[^a-zA-Z0-9]+/g, '-');
    const bundleMapPath =
      `${VARIANT_DIR}/core-js-3-only-polyfill/${folder}/main.bundle.browserify.min.js.map`;
    /** @type {LH.Artifacts.RawSourceMap} */
    const bundleMap = JSON.parse(fs.readFileSync(bundleMapPath, 'utf-8'));
    polyfillDependencies.set(name, bundleMap.sources.filter(s => s.startsWith('node_modules')));
  }

  return polyfillDependencies;
}
Computes a mapping of polyfill names to their list of dependencies.
@return {Map<string, string[]>}