Simplify Makefiles for Packages

These now inherit from a top-level package.mk
Options like use of the network can be enabled on a per package basis
This removes a lot of duplicate code and make the maintenace of these
Makefiles much easier

Signed-off-by: Dave Tucker <dt@docker.com>

pkg/qemu-ga/Makefile

@@ -1,14 +1,3 @@
-.PHONY: tag push
+include ../package.mk
 
-ORG?=linuxkit
 IMAGE=qemu-ga
-
-HASH?=$(shell git ls-tree HEAD -- ../$(notdir $(CURDIR)) | awk '{print $$3}')
-
-default: push
-
-tag: Dockerfile
-	docker build --network=none -t $(ORG)/$(IMAGE):$(HASH) .
-
-push: tag
-	docker pull $(ORG)/$(IMAGE):$(HASH) || docker push $(ORG)/$(IMAGE):$(HASH)