Use cmake's ability to embed frameworks/dylibs (ffmpeg on iOS)

XCode has convenient interface which allows to embed external frameworks/dylibs and set runpath search path (which will e.g. point to bundle/Frameworks). cmake allegedly is able to do this too, e.g.: https://cmake.org/cmake/help/latest/prop_tgt/BUILD_RPATH.html and https://cmake.org/cmake/help/latest/prop_tgt/XCODE_EMBED_type.html. Either this should be documented with example, or our scripts must be updated to use these features if appropriate.