Create static binary for both amd64 and arm64

[jorgebay]

We should provide static binaries of PolarStreams and document how to install it manually on a linux instance.

To support both amd64 and arm64 we could build them inside containers and then copy them using:

docker create --name dummy IMAGE_NAME
docker cp dummy:/path/to/file /dest/to/file
docker rm -f dummy

On amd64, we can just disable CGO_ENABLED:

CGO_ENABLED=0 go build -ldflags '-s -linkmode external -extldflags=-static' .

But arm64 requires musl.