* Cache emitted library translation units
- Restore cached C and LLVM translation units on semantic library cache hits while refreshing volatile build identity
- Rebase public C source annotations and strip them from stable native-cache inputs
* Fix cached library source annotations
* Fix cached C source annotations
* Fix cached C newline annotations
* Split volatile library identity code
- Emit build identity getters from a tiny standalone C translation unit
- Cache generated library program objects independently of volatile identity and archives
- Preserve toolchain, runtime, and translation-unit dependency invalidation coverage
* Preserve library identity during localization
* Keep library identity sources private
* Preserve library identity in public emission
* Preserve identity in kept library units