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/sdk/DEPS b/sdk/DEPS
new file mode 100644
index 0000000..1bb7a2f
--- /dev/null
+++ b/sdk/DEPS
@@ -0,0 +1,6 @@
+include_rules = [
+  "+WebRTC",
+  "+webrtc/api",
+  "+webrtc/media",
+  "+webrtc/system_wrappers",
+]