chore: update makefile from template

Author: soerenmartius

Makefile

@@ -1,7 +1,7 @@
 # Set default shell to bash
 SHELL := /bin/bash -o pipefail
 
-BUILD_TOOLS_VERSION      ?= v0.13.0
+BUILD_TOOLS_VERSION      ?= v0.14.3
 BUILD_TOOLS_DOCKER_REPO  ?= mineiros/build-tools
 BUILD_TOOLS_DOCKER_IMAGE ?= ${BUILD_TOOLS_DOCKER_REPO}:${BUILD_TOOLS_VERSION}
 
@@ -59,6 +59,13 @@ ifdef AWS_ACCESS_KEY_ID
   DOCKER_AWS_FLAGS += -e AWS_SESSION_TOKEN
 endif
 
+# If GOOGLE_CREDENTIALS is defined, we are likely running inside a GCP provider
+# module. To enable GCP authentication inside the docker container, we inject
+# the relevant environment variables (service-account key file).
+ifdef GOOGLE_CREDENTIALS
+	DOCKER_GCP_FLAGS += -e GOOGLE_CREDENTIALS
+endif
+
 # If GITHUB_OWNER is defined, we are likely running inside a GitHub provider
 # module. To enable GitHub authentication inside the docker container,
 # we inject the relevant environment variables.
@@ -87,12 +94,19 @@ test/pre-commit:
 test/unit-tests: DOCKER_FLAGS += ${DOCKER_SSH_FLAGS}
 test/unit-tests: DOCKER_FLAGS += ${DOCKER_GITHUB_FLAGS}
 test/unit-tests: DOCKER_FLAGS += ${DOCKER_AWS_FLAGS}
+test/unit-tests: DOCKER_FLAGS += ${DOCKER_GCP_FLAGS}
+test/unit-tests: DOCKER_FLAGS += $(shell env | grep ^TF_VAR_ | cut -d = -f 1 | xargs -i printf ' -e {}')
 test/unit-tests: DOCKER_FLAGS += -e TF_DATA_DIR=.terratest
 test/unit-tests: TEST ?= "TestUnit"
 test/unit-tests:
 	@echo "${YELLOW}[TEST] ${GREEN}Start Running Go Tests in Docker Container.${RESET}"
 	$(call go-test,./test -run $(TEST))
 
+## Generate README.md with Terradoc
+.PHONY: terradoc
+terradoc:
+	$(call quiet-command,terradoc -o README.md README.tfdoc.hcl)
+
 ## Clean up cache and temporary files
 .PHONY: clean
 clean:
@@ -116,11 +130,6 @@ help:
 	} \
 	{ lastLine = $$0 }' $(MAKEFILE_LIST)
 
-## Generate README.md with Terradoc
-.PHONY: terradoc
-terradoc:
-	$(call quiet-command,terradoc -o README.md README.tfdoc.hcl)
-
 # Define helper functions
 DOCKER_FLAGS   += ${DOCKER_RUN_FLAGS}
 DOCKER_RUN_CMD  = docker run ${DOCKER_FLAGS} ${BUILD_TOOLS_DOCKER_IMAGE}