docker: add hubble CLI binary to the base cilium image

This increases the size of the cilium image by ~12MB (from 408MB to
420MB) but on the other end provides a tailor-made tool to troubleshoot
network issues.
It is expected that once Hubble Relay is GA, having the hubble CLI
binary as part of the base image will no longer be necessary.

Signed-off-by: Robin Hahling <robin.hahling@gw-computing.net>

Dockerfile

@@ -6,6 +6,13 @@ FROM quay.io/cilium/cilium-envoy:a3385205ad620550b35d3b0b651e40898386e6e3 as cil
 ARG CILIUM_SHA=""
 LABEL cilium-sha=${CILIUM_SHA}
 
+#
+# Hubble CLI
+#
+FROM quay.io/cilium/hubble:v0.6.0 as hubble
+ARG CILIUM_SHA=""
+LABEL cilium-sha=${CILIUM_SHA}
+
 #
 # Cilium incremental build. Should be fast given builder-deps is up-to-date!
 #
@@ -49,6 +56,7 @@ LABEL cilium-sha=${CILIUM_SHA}
 LABEL maintainer="maintainer@cilium.io"
 COPY --from=builder /tmp/install /
 COPY --from=cilium-envoy / /
+COPY --from=hubble /usr/bin/hubble /usr/bin/hubble
 COPY --from=builder /go/src/github.com/cilium/cilium/plugins/cilium-cni/cni-install.sh /cni-install.sh
 COPY --from=builder /go/src/github.com/cilium/cilium/plugins/cilium-cni/cni-uninstall.sh /cni-uninstall.sh
 COPY --from=builder /go/src/github.com/cilium/cilium/contrib/packaging/docker/init-container.sh /init-container.sh