There was a post in the 4.5 announcement thread. Here is what to do.
"Quote Originally Posted by Josh Adams View Post
Hey there guys. Here’s some more info on the 3.1 stuff.
Do to the way 3.1 support works, it needs a separately compiled executable. We are investigating a way to have ES3.1+AES support and ES2 support compiled in the same code, but for now it needs separate code.
Since we didn’t want to inflate the Android library/binary download size quite yet, we did not release ES31 binaries. If you want to play with it, you will need to compile the code yourself with support for it. It is controlled by this .ini section (you should have one in your project’s DefaultEngine.ini).
We didn’t expose this in the editor since it isn’t quite ready. If you have both of those set to true, it will compile 2 times for each source file. There is one final issue with it where both ES2 and ES31 will link to the same executable, as the fix for it will cause other issues (we will need to query GL support from Java before we load our C++ code, which is a bit tricky). I would highly recommend turning on es31 and turning off es2 for now.
Hope this helps!
FYI the Nexus Player announced on wednesday uses an Intel processor instead of the K1. Right now the only announced K1 devices are 3 tablets (Nexus 9, Nvideas own, and the MiiPad).