1. Run yarn
2. Run yarn ngcc --create-ivy-entry-points
3. Inspect node_modules/@angular/core/__ivy_ngcc__/bundles/core.umd.js

Notice how there are multiple trailing commas in expressions that cause syntax errors in IE11.

typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports, require('rxjs'), require('rxjs/operators'),) :