Add a new Makefile variable to override DockerInDocker engine version…

… we use to run e2e tests

Signed-off-by: Silvin Lubecki <silvin.lubecki@docker.com>

docker.Makefile

@@ -16,12 +16,13 @@ LINTER_IMAGE_NAME = docker-cli-lint$(IMAGE_TAG)
 CROSS_IMAGE_NAME = docker-cli-cross$(IMAGE_TAG)
 VALIDATE_IMAGE_NAME = docker-cli-shell-validate$(IMAGE_TAG)
 E2E_IMAGE_NAME = docker-cli-e2e$(IMAGE_TAG)
+E2E_ENGINE_VERSION ?=
 CACHE_VOLUME_NAME := docker-cli-dev-cache
 ifeq ($(DOCKER_CLI_GO_BUILD_CACHE),y)
 DOCKER_CLI_MOUNTS += -v "$(CACHE_VOLUME_NAME):/root/.cache/go-build"
 endif
 VERSION = $(shell cat VERSION)
-ENVVARS = -e VERSION=$(VERSION) -e GITCOMMIT -e PLATFORM -e TESTFLAGS -e TESTDIRS -e GOOS -e GOARCH -e GOARM
+ENVVARS = -e VERSION=$(VERSION) -e GITCOMMIT -e PLATFORM -e TESTFLAGS -e TESTDIRS -e GOOS -e GOARCH -e GOARM -e TEST_ENGINE_VERSION=$(E2E_ENGINE_VERSION)
 
 # build docker image (dockerfiles/Dockerfile.build)
 .PHONY: build_docker_image
@@ -149,7 +150,7 @@ test-e2e-experimental: build_e2e_image # run experimental e2e tests
 
 .PHONY: test-e2e-non-experimental
 test-e2e-non-experimental: build_e2e_image # run non-experimental e2e tests
-	docker run --rm -v /var/run/docker.sock:/var/run/docker.sock $(ENVVARS) $(E2E_IMAGE_NAME)
+	docker run --rm -v /var/run/docker.sock:/var/run/docker.sock $(ENVVARS) -e TEST_ENGINE_VERSION=$(E2E_ENGINE_VERSION) $(E2E_IMAGE_NAME)
 
 .PHONY: test-e2e-connhelper-ssh
 test-e2e-connhelper-ssh: build_e2e_image # run experimental SSH-connection helper e2e tests