Build dynamic framework with podspec for Objective-C API.

webrtc/base/objc/RTCFieldTrials.mm

 /*
  *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #import "webrtc/base/objc/RTCFieldTrials.h"
 
 #include <memory>
 #include "webrtc/system_wrappers/include/field_trial_default.h"
 
-#import <Foundation/Foundation.h>
 #import "webrtc/base/objc/RTCLogging.h"
 
 static NSString * const kRTCEnableSendSideBweString =
     @"WebRTC-SendSideBwe/Enabled/";
 static std::unique_ptr<char[]> gFieldTrialInitString;
 
 void RTCInitFieldTrials(RTCFieldTrialOptions options) {
   NSMutableString *fieldTrialInitString = [NSMutableString string];
   if (options & RTCFieldTrialOptionsSendSideBwe) {
     [fieldTrialInitString appendString:kRTCEnableSendSideBweString];
   }
   size_t len = fieldTrialInitString.length + 1;
   gFieldTrialInitString.reset(new char[len]);
   if (![fieldTrialInitString getCString:gFieldTrialInitString.get()
                               maxLength:len
                                encoding:NSUTF8StringEncoding]) {
     RTCLogError(@"Failed to convert field trial string.");
     return;
   }
   webrtc::field_trial::InitFieldTrialsFromString(gFieldTrialInitString.get());
 }