Fix makefile to default variables properly

calico_node/Makefile

@@ -2,33 +2,33 @@
 # Versions:
 RELEASE_STREAM?=v2.4
 
-GO_BUILD_VER:=v0.7
+GO_BUILD_VER?=v0.7
 CALICO_BUILD?=calico/go-build:$(GO_BUILD_VER)
 
 CALICO_NODE_DIR=$(dir $(realpath $(lastword $(MAKEFILE_LIST))))
 VERSIONS_FILE?=$(CALICO_NODE_DIR)/../_data/versions.yml
 
 # For local builds this can be made faster by running "go get github.com/mikefarah/yaml" and changing YAML_CMD to "yaml"
 YAML_CMD?=$(shell which yaml || echo docker run --rm -i $(CALICO_BUILD) yaml)
-CALICO_VER := $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].title')
+CALICO_VER ?= $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].title')
 CALICO_GIT_VER ?= $(shell git describe --tags --dirty --always)
-BIRD_VER := $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.calico-bird.version')
-GOBGPD_VER := $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.calico-bgp-daemon.version')
-FELIX_VER := $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.felix.version')
-CALICOCTL_VER := $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.calicoctl.version')
-LIBNETWORK_PLUGIN_VER := $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.libnetwork-plugin.version')
-TYPHA_VER := $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.typha.version')
-K8S_POLICY_VER := $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.calico/kube-policy-controller.version')
-CNI_VER := $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.calico/cni.version')
+BIRD_VER ?= $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.calico-bird.version')
+GOBGPD_VER ?= $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.calico-bgp-daemon.version')
+FELIX_VER ?= $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.felix.version')
+CALICOCTL_VER ?= $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.calicoctl.version')
+LIBNETWORK_PLUGIN_VER ?= $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.libnetwork-plugin.version')
+TYPHA_VER ?= $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.typha.version')
+K8S_POLICY_VER ?= $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.calico/kube-policy-controller.version')
+CNI_VER ?= $(shell cat $(VERSIONS_FILE) | $(YAML_CMD) read - '"$(RELEASE_STREAM)".[0].components.calico/cni.version')
 # TODO - Why isn't confd in versions.yaml
-CONFD_VER := v0.12.1-calico0.2.0
+CONFD_VER ?= v0.12.1-calico0.2.0
 
-SYSTEMTEST_CONTAINER_VER := latest
+SYSTEMTEST_CONTAINER_VER ?= latest
 # we can use "custom" build image and test image name
 SYSTEMTEST_CONTAINER?=calico/test:$(SYSTEMTEST_CONTAINER_VER)
 
 # Ensure that the dist directory is always created
-MAKE_SURE_BIN_EXIST := $(shell mkdir -p dist)
+MAKE_SURE_BIN_EXIST ?= $(shell mkdir -p dist)
 
 ###############################################################################
 # URL for Calico binaries
@@ -475,11 +475,11 @@ release: clean
 	@echo "git push origin $(CALICO_VER)"
 
 
-RELEASE_DIR:=release-$(CALICO_VER)
-RELEASE_DIR_K8S_MANIFESTS:=$(RELEASE_DIR)/k8s-manifests
-RELEASE_DIR_IMAGES:=$(RELEASE_DIR)/images
-RELEASE_DIR_BIN:=$(RELEASE_DIR)/bin
-MANIFEST_SRC := ../_site/$(RELEASE_STREAM)/getting-started/kubernetes/installation
+RELEASE_DIR?=release-$(CALICO_VER)
+RELEASE_DIR_K8S_MANIFESTS?=$(RELEASE_DIR)/k8s-manifests
+RELEASE_DIR_IMAGES?=$(RELEASE_DIR)/images
+RELEASE_DIR_BIN?=$(RELEASE_DIR)/bin
+MANIFEST_SRC ?= ../_site/$(RELEASE_STREAM)/getting-started/kubernetes/installation
 
 ## Create an archive that contains a complete "Calico" release
 release-archive: $(RELEASE_DIR).tgz