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}
diff --git a/webrtc/examples/objc/AppRTCDemo/ARDAppEngineClient.m b/webrtc/examples/objc/AppRTCDemo/ARDAppEngineClient.m
index 7d8a185..0ba32c4 100644
--- a/webrtc/examples/objc/AppRTCDemo/ARDAppEngineClient.m
+++ b/webrtc/examples/objc/AppRTCDemo/ARDAppEngineClient.m
@@ -10,7 +10,7 @@
 
 #import "ARDAppEngineClient.h"
 
-#import "webrtc/base/objc/RTCLogging.h"
+#import "WebRTC/RTCLogging.h"
 
 #import "ARDJoinResponse.h"
 #import "ARDMessageResponse.h"