[Cronet] Build static libcronet.a for iOS with complete dependencies.

components/cronet/ios/sample/main.mm

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import <Foundation/Foundation.h>
+#import <UIKit/UIKit.h>
+
+#import "cronet_sample_app_delegate.h"
+
+int main(int argc, char* argv[]) {
+  @autoreleasepool {
+    return UIApplicationMain(
+        argc, argv, nil, NSStringFromClass([CronetSampleAppDelegate class]));
+  }
+}