fix(@angular/cli): only force CommonJS if module kind is ES2015

Author: clydin

Diff for: packages/@angular/cli/models/webpack-config.ts

@@ -48,6 +48,11 @@ export class NgCliWebpackConfig<T extends BuildOptions = BuildOptions> {
     const supportES2015 = tsConfig.options.target !== projectTs.ScriptTarget.ES3
                         && tsConfig.options.target !== projectTs.ScriptTarget.ES5;
 
+    // Only force if the default module kind is used (ES2015)
+    // Allows user to adjust module kind (to esNext for example)
+    buildOptions.forceTsCommonjs = buildOptions.forceTsCommonjs
+                                 && tsConfig.options.module === projectTs.ModuleKind.ES2015;
+
     this.wco = { projectRoot, buildOptions, appConfig, tsConfig, supportES2015 };
   }