Passing Circle environment variables to make

Build Environment
1

I can’t figure out how to pass circle environment variables to my Makefile using a machine executor.

PROJECT_NAME           ?= studyclever
PROJECT                ?= wundertax/$(PROJECT_NAME)
BUILD_TAG              ?= build-local
DOCKER_USER            ?= bogus
DOCKER_PASS            ?= pogus

SERVER_IMAGE_TAG 					= $(PROJECT):$(BUILD_TAG)
TEST_IMAGE_TAG 						= $(SERVER_IMAGE_TAG)-tests
ASSETS_IMAGE_TAG					= $(PROJECT)-assets:$(BUILD_TAG)

export TEST_IMAGE_TAG
export SERVER_IMAGE_TAG
export ASSET_IMAGE_TAG

build-server:
	docker login -u ${DOCKER_USER} -p ${DOCKER_PASS}

	docker build \
		--tag $(SERVER_IMAGE_TAG) \
		--build-arg RAILS_ENV=${RAILS_ENV} \
		--build-arg BUNDLE_WITHOUT="test development" \
		--build-arg FOLDERS_TO_REMOVE="spec node_modules app/assets vendor/assets lib/assets tmp/cache vendor/yarn" \
		--target Final \
		--file Dockerfile \
		.

The environment variable for BUILD_TAG, DOCKER_USER and DOCKER_PASS should be provided by circle. Do I need to set some specific shell or source some specific file inside make to make this work?