Build dynamic iOS SDK.

- Places most ObjC code into webrtc/sdk/objc instead.
- New gyp targets to build, strip and export symbols for dylib.
- Removes old script used to generate dylib.

BUG=

Review URL: https://codereview.webrtc.org/1903663002

Cr-Commit-Position: refs/heads/master@{#12524}

webrtc/sdk/objc/Framework/Classes/RTCVideoRendererAdapter.h

@@ -0,0 +1,27 @@
+/*
+ *  Copyright 2015 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 <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/*
+ * Creates a rtc::VideoSinkInterface surface for an RTCVideoRenderer. The
+ * rtc::VideoSinkInterface is used by WebRTC rendering code - this
+ * adapter adapts calls made to that interface to the RTCVideoRenderer supplied
+ * during construction.
+ */
+@interface RTCVideoRendererAdapter : NSObject
+
+- (instancetype)init NS_UNAVAILABLE;
+
+@end
+
+NS_ASSUME_NONNULL_END