services/internal/packages: turn on compression for zip packages
services/internal/packages: turn on compression for zip packages

Without the Method field set in the header, the zip library creates an
uncompressed archive, similar to a tar.

Change-Id: Iee963a1ff0683d96803a976de546cb97d9a820ba

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref