fix(@angular-devkit/build-angular): dont serve files on cwd (#12547)

Author: filipesilva

packages/angular_devkit/build_angular/src/dev-server/index.ts

@@ -227,6 +227,7 @@ export class DevServerBuilder implements Builder<DevServerBuilderOptions> {
       disableHostCheck: options.disableHostCheck,
       publicPath: servePath,
       hot: options.hmr,
+      contentBase: false,
     };
 
     if (options.ssl) {

packages/angular_devkit/build_angular/test/dev-server/works_spec_large.ts

@@ -34,4 +34,16 @@ describe('Dev Server Builder', () => {
       take(1),
     ).toPromise().then(done, done.fail);
   }, 30000);
+
+  it(`doesn't serve files on the cwd directly`, async () => {
+    const res = await runTargetSpec(host, devServerTargetSpec).pipe(
+      tap((buildEvent) => expect(buildEvent.success).toBe(true)),
+      // When webpack-dev-server doesn't have `contentBase: false`, this will serve the repo README.
+      concatMap(() => from(request('http://localhost:4200/README.md'))),
+      take(1),
+    ).toPromise();
+
+    expect(res).not.toContain('This file is automatically generated during release.');
+    expect(res).toContain('<title>HelloWorldApp</title>');
+  });
 });