The errors you are getting in the second file, related to: LogFMOD: Loading plugin ‘libOculusSpatializerFMOD’, can be fixed by changing the plugin name in FMOD’s Unreal settings to “OculusSpatializerFMOD”.
The other errors I am not sure about. After some searching on the Unreal answers hub, it looks like it may be to do the android SDK. I am able to build without getting those errors.
Note that 4.15 has a lot of core changes to audio engine, so maybe FMOD plugin needs a bit more of an overhaul to make it work with UE 4.15 and upcoming UE 4.16 (where whole audio system will be replaced). This is a really big issue for us, Gear VR devs, and we would definitely appreciate if it was resolved in 4.15.