Move Makefile.bundled-shared from openwebrtc.recipe to openwebrtc.git

Currently, in post_install, the openwebrtc recipe re-creates (Android-specific) libopenwebrtc_jni.so and libopenwebrtc_bridge_jni.so such that all the dependency libraries are linked in statically. We should do this using autotools inside openwebrtc.git. This needs to be done using a specially-crafted linker command (which is done by Makefile.bundled-shared) since there is no way to force libtool to do this. It will always choose the shared library over the static library if both are available while satisfying a dependency.

This wasn't a problem with OpenWebRTC's build scripts because all the dependencies were only built statically.

This change depends on us moving to Cerbero as the primary build system (#222)

ref: https://github.com/nirbheek/cerbero/pull/11/

Start by reviewing the openwebrtc recipe's post_install step and the existing Makefile.bundled-shared, then check the Cerbero migration tracked in #222. Move the Android-specific shared-library linking into openwebrtc.git using the existing linker approach, and confirm the recipe no longer recreates libopenwebrtc_jni.so or libopenwebrtc_bridge_jni.so.

Written by the indexing model from the issue text.