redirect Copilot cache to service state Set XDG_CACHE_HOME from the configured inference state so the systemd service can extract Copilot outside its protected home directory. Co-authored-by: Copilot <[email protected]>

The files in this directory are only used during the build process of LuaJIT.
For cross-compilation, they must be executed on the host, not on the target.

These files should NOT be installed!