I had the same problem when I was trying to develop a prototype app that needed the 3D audio capabilities.
I didn't go as far as you did with compiling my own android source, but thought of that. Back ten I came across an Android compiled openal library here on SOF. As had to drop the project for an other one I started to look at the problem again last week. What I found was this:
http://www.am3d.co.jp/home-english/products/3d-audio/hardwaresoftware-platforms/android.aspx
It seems to be the missing link but has to be licenced for your app. Maybe this is helpful for you. I says the folowing on their website "The implementation realizes the missing 3D audio functionality in the Android OpenSL ES implementation." However even if it says "The API is AM3D's simple and proprietary API." the technical documentation seems to show off, that you are programming the 3D effects themself in the standard OpenSL ES way.