## Why
Native voice libraries need package-relative loader paths so a prepared runtime
can be moved without retaining references to its build prefix.
## What changed
- Configure CMake and GNU Linux Meson builds with relative runtime paths, while
also setting relocatable install names and paths for CMake libraries on macOS.
- Add a GNU Linux runtime preparer for x64 and ARM64 that validates bounded ELF64
metadata, selects the declared GStreamer plugins and dependency closure, and
preserves the `lib/gstreamer-1.0/` layout.
- Reject malformed ELF metadata, path-bearing imports, unsupported loader
dependencies, and native outputs that still contain incompatible runtime
paths.
## Testing
Add native tests for relative build paths, relocated library loading, dependency
and digest failures, malformed ELF inputs, and cleanup after failed preparation.
GitOrigin-RevId: ed94819b07d20214b56363446b64f765e08d75fa
