* Enables module-mode in Docker to fix build
* Statically compile binary in Docker to fix missing dependency errors
* Ensure target OS is set to Linux for Docker builds
Use debian/distroless (glibc) as a base which in general gives
slightly higher performance than alpine (musl) while trading
off container size (about 10mb).
The build phase makes the assumption that any capnproto-files
are pre-processed before building in-docker.