Add a way to just build windows and osx

Signed-off-by: Eli Uriegas <eli.uriegas@docker.com>

Makefile

@@ -34,6 +34,14 @@ binary: ## build executable for Linux
 cross: ## build executable for macOS and Windows
 	./scripts/build/cross
 
+.PHONY: binary-windows
+binary-windows: ## build executable for Windows
+	./scripts/build/windows
+
+.PHONY: binary-osx
+binary-osx: ## build executable for macOS
+	./scripts/build/osx
+
 .PHONY: dynbinary
 dynbinary: ## build dynamically linked binary
 	./scripts/build/dynbinary

docker.Makefile

@@ -54,6 +54,14 @@ test: test-unit test-e2e
 cross: build_cross_image
 	docker run --rm $(ENVVARS) $(MOUNTS) $(CROSS_IMAGE_NAME) make cross
 
+.PHONY: binary-windows
+binary-windows: build_cross_image
+	docker run --rm $(ENVVARS) $(MOUNTS) $(CROSS_IMAGE_NAME) make $@
+
+.PHONY: binary-osx
+binary-osx: build_cross_image
+	docker run --rm $(ENVVARS) $(MOUNTS) $(CROSS_IMAGE_NAME) make $@
+
 .PHONY: watch
 watch: build_docker_image
 	docker run --rm $(ENVVARS) $(MOUNTS) $(DEV_DOCKER_IMAGE_NAME) make watch