Address build warning fixes.

rollup.config.js

@@ -54,5 +54,11 @@ export default [
       format: 'es',
     },
     plugins: [...plugins],
+    // These two files use this at the toplevel, which causes rollup warning
+    // spam on build: `this` has been rewritten to `undefined`
+    moduleContext: {
+      './node_modules/@formatjs/intl-utils/lib/src/diff.js': 'window',
+      './node_modules/@formatjs/intl-utils/lib/src/resolve-locale.js': 'window',
+    },
   },
 ];