Rename "tag*" Makefile targets to "build*"

This better matches the `linuxkit pkg build` nomenclature.

Signed-off-by: Ian Campbell <ijc@docker.com>

tools/Makefile

@@ -4,7 +4,7 @@ DIRS = $(dir $(shell find . -maxdepth 2 -mindepth 2 -type f -name build.yml))
 # Note that these are only recursed on for the push target which was the historical behaviour.
 MAKEDIRS = alpine guestfs
 
-.PHONY: push forcepush tag forcetag show-tag clean
+.PHONY: push forcepush build forcebuild show-tag clean
 
 push:
 	@set -e; for d in $(DIRS); do linuxkit pkg push "$$d"; done
@@ -13,10 +13,10 @@ push:
 forcepush:
 	@set -e; for d in $(DIRS); do linuxkit pkg push --force "$$d"; done
 
-tag:
+build:
 	@set -e; for d in $(DIRS); do linuxkit pkg build "$$d"; done
 
-forcetag:
+forcebuild:
 	@set -e; for d in $(DIRS); do linuxkit pkg build --force "$$d"; done
 
 show-tag:

tools/alpine/Makefile

@@ -1,4 +1,4 @@
-.PHONY: tag push
+.PHONY: build push
 
 ORG?=linuxkit
 IMAGE=alpine
@@ -61,7 +61,7 @@ push: hash iid versions.$(ARCH)
 	./push-manifest.sh $(ORG) $(IMAGE)
 	rm -f iid
 
-tag: hash iid versions.$(ARCH)
+build: hash iid versions.$(ARCH)
 	docker pull $(ORG)/$(IMAGE):$(shell cat hash) || \
 		docker tag $(shell cat iid) $(ORG)/$(IMAGE):$(shell cat hash)
 	rm -f iid

tools/guestfs/Makefile

@@ -1,4 +1,4 @@
-.PHONY: tag push
+.PHONY: build push
 
 IMAGE=guestfs
 
@@ -18,7 +18,7 @@ push: hash iid
 		 docker push linuxkit/$(IMAGE):$(shell cat hash))
 	rm -f iid
 
-tag: hash iid
+build: hash iid
 	docker pull linuxkit/$(IMAGE):$(shell cat hash) || \
 		docker tag $(shell cat iid) linuxkit/$(IMAGE):$(shell cat hash)
 	rm -f iid