Always create fresh build context

Avoid leftover files leaking into build context when compiling Docker
images.

Makefile

@@ -1,20 +1,23 @@
 tag := $(shell git rev-parse --short --verify HEAD)
 all: dev:=0
-all:
+all: build push
+
+.PHONY: build
+build:
 	cd app && $(MAKE) dev=${dev} tag=${tag}
 	cd agent && $(MAKE) dev=${dev} tag=${tag}
 	cd monitor && $(MAKE) dev=${dev} tag=${tag}
 	cd charts && $(MAKE) dev=${dev} tag=${tag}
+
+.PHONY: push
+push:
 ifneq (1,$(dev))
-	$(MAKE) push
-else
+	$(MAKE) push-dev
 	docker push skep/agent:dev
 	docker push skep/monitor:dev
 	docker push skep/app:dev
 	docker push skep/charts:dev
-endif
-
-push:
+else
 	docker push skep/agent:${tag}
 	docker push skep/monitor:${tag}
 	docker push skep/app:${tag}
@@ -23,3 +26,4 @@ push:
 	docker push skep/monitor:latest
 	docker push skep/app:latest
 	docker push skep/charts:latest
+endif

app/Makefile

@@ -3,6 +3,7 @@ all:
 	mkdir -p .build/
 ifeq (${dev},1)
 	cp Dockerfile Pipfile Pipfile.lock .build/
+	rm -f .build/build.tar
 	tar zcf .build/build.tar --exclude build.tar  --exclude .build --exclude node_modules .
 	cp -r ../shared/skep .build/skep
 	cd .build/ && docker build . -t skep/app:dev