fix(compiler): walk third party modules (#12453)

fixes #11889
fixes #12428

modules/@angular/compiler-cli/integrationtest/third_party_src/module.ts

@@ -0,0 +1,28 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {NgModule} from '@angular/core';
+
+import {ThirdPartyComponent} from './comp';
+import {ThirdPartyDirective} from './directive';
+import {AnotherThirdPartyModule} from './other_module';
+
+@NgModule({
+  declarations: [
+    ThirdPartyComponent,
+    ThirdPartyDirective,
+  ],
+  exports: [
+    AnotherThirdPartyModule,
+    ThirdPartyComponent,
+    ThirdPartyDirective,
+  ],
+  imports: [AnotherThirdPartyModule]
+})
+export class ThirdpartyModule {
+}