skel2: Add Rust staticlib dependency

Adds a rust staticlib with a proc-macro dependency to reproduce broken
linking behavior. Adds the skel2 app to the build to exercise this in
CI.

Test: build.py generic-arm64-test-debug
Bug: 323999436

Change-Id: I5ff43173c3ae3e71bbbd950294d50b07da6d8b4a
5 files changed