Amend Makefile

Added --platform flag to enable container build on M* machines. Also
added descriptions to increase visibility of options and to bring inline
with other repos.

Makefile

@@ -2,10 +2,16 @@
 include .env
 export
 
-build:
+.DEFAULT_GOAL := help
+
+.PHONY: build
+build: ## Get blackbox_exporter image from GitHub and build
 	./build.sh
 
-run: build
+.PHONY: run
+run: ## Get blackbox_exporter image from GitHub, build and run against target in .env
+	$(MAKE) build
 	docker run -it -e PROM_USER=$$PROM_USER -e PROM_PASS=$$PROM_PASS -e PROM_TARGET=$$PROM_TARGET -e REMOTE_WRITE_URL=$$REMOTE_WRITE_URL app-reachability:latest
 
-.PHONY: build run
+help:
+	@grep -h -E '^[a-zA-Z0-9_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'

build.sh

@@ -7,4 +7,4 @@ tar -xzvf tmp/bb.tar.gz -C ./tmp
 mkdir -p build
 mv ./tmp/blackbox_exporter-0.19.0.linux-amd64/blackbox_exporter ./build
 
-docker build -t app-reachability .
+docker build --platform linux/amd64 -t app-reachability .