Add keymaster app to userspace library build system

Switch to building keymaters and its tests with the trusted_app.mk
system instead of as a generic lk module. This allows the app to depend
on common userspace static libraries.

Test: build.py qemu-generic-arm64-test-debug
Bug: 169448829
Change-Id: I8e35a6f6fe90d7440377d45d6dee8b096e18fc3c
3 files changed