I was able to package for armv7 and arm64 today, using UE 4.15.0, on macOS 10.12.3 and Xcode 8.2.1.
Two things I hadn’t tried before was making sure OpenGL ES support was enabled, and “Generate Xcode archive package” was enabled. Not sure if the archive package will make a difference, but armv7 devices don’t support Metal, so they need OpenGL ES.
Here’s the build settings I used:
