fix(packages): use ES modules for primary build (#11120)

modules/@angular/compiler-cli/test/mocks.ts

@@ -6,10 +6,9 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {ReflectorHostContext} from '@angular/compiler-cli/src/reflector_host';
 import * as ts from 'typescript';
 
-import {ReflectorHostContext} from '../src/reflector_host';
-
 export type Entry = string | Directory;
 
 export interface Directory { [name: string]: Entry; }
@@ -61,6 +60,15 @@ export class MockContext implements ReflectorHostContext {
     }
     return current;
   }
+
+  getDirectories(path: string): string[] {
+    const dir = this.getEntry(path);
+    if (typeof dir !== 'object') {
+      return [];
+    } else {
+      return Object.keys(dir).filter(key => typeof dir[key] === 'object');
+    }
+  }
 }
 
 function normalize(parts: string[]): string[] {
@@ -117,4 +125,6 @@ export class MockCompilerHost implements ts.CompilerHost {
   useCaseSensitiveFileNames(): boolean { return false; }
 
   getNewLine(): string { return '\n'; }
+
+  getDirectories(path: string): string[] { return this.context.getDirectories(path); }
 }