add support for custom CI build commands via $CUSTOM_CMD

.travis.yml

@@ -42,6 +42,8 @@ install:
 
 script:
   - set -e # fail fast
+  # check if the build environment contains a special command via $CUSTOM_CMD
+  - if [ "$CUSTOM_CMD" = rebuild-base-image ]; then make docker-build-base-ci; exit; fi
   # run tests using Python 3 (limit the set of tests to reduce test duration)
   - DEBUG=1 LAMBDA_EXECUTOR=docker USE_SSL=1 TEST_ERROR_INJECTION=1 TEST_PATH="tests/integration/test_lambda.py tests/integration/test_integration.py" make test
   # start pulling Docker base image in the background

Makefile

@@ -3,6 +3,7 @@ IMAGE_NAME_BASE ?= localstack/java-maven-node-python
 IMAGE_NAME_LIGHT ?= localstack/localstack-light
 IMAGE_NAME_FULL ?= localstack/localstack-full
 IMAGE_TAG ?= $(shell cat localstack/constants.py | grep '^VERSION =' | sed "s/VERSION = ['\"]\(.*\)['\"].*/\1/")
+DOCKER_SQUASH ?= --squash
 VENV_DIR ?= .venv
 PIP_CMD ?= pip
 TEST_PATH ?= .
@@ -60,10 +61,15 @@ docker-squash:
 		docker-squash -t $(IMAGE_NAME):$(IMAGE_TAG) $(IMAGE_NAME):$(IMAGE_TAG)
 
 docker-build-base:
-	docker build --squash -t $(IMAGE_NAME_BASE) -f bin/Dockerfile.base .
+	docker build $(DOCKER_SQUASH) -t $(IMAGE_NAME_BASE) -f bin/Dockerfile.base .
 	docker tag $(IMAGE_NAME_BASE) $(IMAGE_NAME_BASE):$(IMAGE_TAG)
 	docker tag $(IMAGE_NAME_BASE):$(IMAGE_TAG) $(IMAGE_NAME_BASE):latest
 
+docker-build-base-ci:
+	DOCKER_SQUASH= make docker-build-base
+	IMAGE_NAME=$(IMAGE_NAME_BASE) IMAGE_TAG=latest make docker-squash
+	docker push $(IMAGE_NAME_BASE):latest
+
 docker-push:       ## Push Docker image to registry
 	make docker-squash
 	docker push $(IMAGE_NAME):$(IMAGE_TAG)