Add iOS static library GN build script. NOTRY=True

webrtc/modules/audio_device/ios/objc/RTCAudioSession.h

 /*
  *  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 <AVFoundation/AVFoundation.h>
 #import <Foundation/Foundation.h>
 
+#import "WebRTC/RTCMacros.h"
+
 NS_ASSUME_NONNULL_BEGIN
 
 extern NSString * const kRTCAudioSessionErrorDomain;
 /** Method that requires lock was called without lock. */
 extern NSInteger const kRTCAudioSessionErrorLockRequired;
 /** Unknown configuration error occurred. */
 extern NSInteger const kRTCAudioSessionErrorConfiguration;
 
 @class RTCAudioSession;
 @class RTCAudioSessionConfiguration;
 
 // Surfaces AVAudioSession events. WebRTC will listen directly for notifications
 // from AVAudioSession and handle them before calling these delegate methods,
 // at which point applications can perform additional processing if required.
+RTC_EXPORT
 @protocol RTCAudioSessionDelegate <NSObject>
 
 @optional
 /** Called on a system notification thread when AVAudioSession starts an
  *  interruption event.
  */
 - (void)audioSessionDidBeginInterruption:(RTCAudioSession *)session;
 
 /** Called on a system notification thread when AVAudioSession ends an
  *  interruption event.
@@ skipping 35 matching lines @@
 
 @end
 
 /** Proxy class for AVAudioSession that adds a locking mechanism similar to
  *  AVCaptureDevice. This is used to that interleaving configurations between
  *  WebRTC and the application layer are avoided.
  *
  *  RTCAudioSession also coordinates activation so that the audio session is
  *  activated only once. See |setActive:error:|.
  */
+RTC_EXPORT
 @interface RTCAudioSession : NSObject
 
 /** Convenience property to access the AVAudioSession singleton. Callers should
  *  not call setters on AVAudioSession directly, but other method invocations
  *  are fine.
  */
 @property(nonatomic, readonly) AVAudioSession *session;
 
 /** Our best guess at whether the session is active based on results of calls to
  *  AVAudioSession.
@@ skipping 118 matching lines @@
 /** Convenience method that calls both setConfiguration and setActive.
  *  |lockForConfiguration| must be called first.
  */
 - (BOOL)setConfiguration:(RTCAudioSessionConfiguration *)configuration
                   active:(BOOL)active
                    error:(NSError **)outError;
 
 @end
 
 NS_ASSUME_NONNULL_END