Add libbinder_ndk to the NDK.

This library is a C API over libbinder. Its intended to be used as a
bakend of AIDL, but implemented services direclty in this protocol is
also possible.

Bug: 111445392
Test: runtests.sh
Change-Id: Iaf3adc0dce0646dcc04e78ae33cccdf0c29d613c