libbinder_rs: Build binder_rpc_unstable_bindgen on Trusty

Add a Trusty build rules.mk file for binder_rpc_unstable,
then build Rust wrappers around binder_rpc_unstable using bindgen.

Bug: 242243245
Test: build on Trusty
Change-Id: I1982d4a70e9bb56c137b02edbc6efcd5c37ef516
6 files changed