Fix docker build recipe

Makefile

@@ -1,4 +1,14 @@
-DOCKER_DATE_TAG := $(shell date +%Y%m%d%H%M)
+DOCKER_DATE_TAG := $(shell date --utc +%Y.%-m.%-d%-H%-M)
+
+YQ_VERSION ?= v4.30.4
+YQ_BINARY ?= yq_linux_amd64
+
+tools: tools/yq/bin/yq
+
+tools/yq/bin/yq:
+	mkdir -p tools/yq/bin
+	wget https://github.com/mikefarah/yq/releases/download/${YQ_VERSION}/${YQ_BINARY} -O tools/yq/bin/yq &&\
+    chmod +x tools/yq/bin/yq
 
 build:
 	CGO_ENABLED=0 go build -v -o bin/fake-smtp ./cmd/fake-smtp
@@ -31,7 +41,7 @@ docker-release:
 test:
 	go test -v -race ./...
 
-release: dist
+release: dist tools
 	@./misc/script/release.sh
 
 dist: