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-Original-Commit-Position: refs/heads/master@{#12524}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 9eeb6240c93efe2219d4d6f4cf706030e00f64d7
diff --git a/DEPS b/DEPS
index 992c32a..ab08fbf 100644
--- a/DEPS
+++ b/DEPS
@@ -29,6 +29,7 @@
   "+webrtc/video_renderer.h",
   "+webrtc/video_send_stream.h",
 
+  "+WebRTC",
   "+webrtc/base",
   "+webrtc/modules/include",
   "+webrtc/test",