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/modules/video_coding/codecs/h264/h264.gypi

@@ -64,7 +64,7 @@
           'type': 'static_library',
           'includes': [ '../../../../build/objc_common.gypi' ],
           'dependencies': [
-            '<(webrtc_root)/base/base.gyp:rtc_base_objc',
+            '<(webrtc_root)/sdk/sdk.gyp:rtc_sdk_common_objc',
           ],
           'link_settings': {
             'xcode_settings': {

webrtc/modules/video_coding/codecs/h264/h264_video_toolbox_decoder.cc

@@ -15,12 +15,12 @@
 
 #include <memory>
 
+#if defined(WEBRTC_IOS)
+#include "RTCUIApplication.h"
+#endif
 #include "libyuv/convert.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
-#if defined(WEBRTC_IOS)
-#include "webrtc/base/objc/RTCUIApplication.h"
-#endif
 #include "webrtc/common_video/include/corevideo_frame_buffer.h"
 #include "webrtc/modules/video_coding/codecs/h264/h264_video_toolbox_nalu.h"
 #include "webrtc/video_frame.h"

webrtc/modules/video_coding/codecs/h264/h264_video_toolbox_encoder.cc

@@ -17,12 +17,12 @@
 #include <string>
 #include <vector>
 
+#if defined(WEBRTC_IOS)
+#include "RTCUIApplication.h"
+#endif
 #include "libyuv/convert_from.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
-#if defined(WEBRTC_IOS)
-#include "webrtc/base/objc/RTCUIApplication.h"
-#endif
 #include "webrtc/modules/video_coding/codecs/h264/h264_video_toolbox_nalu.h"
 #include "webrtc/system_wrappers/include/clock.h"