Add darwin release

Author: jwilder

Makefile

@@ -13,10 +13,13 @@ docker-squash:
 dist-clean:
 	rm -rf dist
 	rm -f docker-squash-linux-*.tar.gz
+	rm -f docker-squash-darwin-*.tar.gz
 
 dist: dist-clean
 	mkdir -p dist/linux/amd64 && GOOS=linux GOARCH=amd64 go build -ldflags "$(LDFLAGS)" -o dist/linux/amd64/docker-squash
+	mkdir -p dist/darwin/amd64 && GOOS=darwin GOARCH=amd64 go build -ldflags "$(LDFLAGS)" -o dist/darwin/amd64/docker-squash
 
 release: dist
 	glock sync github.com/jwilder/docker-squash
 	tar -cvzf docker-squash-linux-amd64-$(TAG).tar.gz -C dist/linux/amd64 docker-squash
+	tar -cvzf docker-squash-darwin-amd64-$(TAG).tar.gz -C dist/darwin/amd64 docker-squash