Update examples collection

emsdk-cache/emsdk-main/docker/Makefile

@@ -0,0 +1,31 @@
+# A Makefile to build, test, tag and publish the Emscripten SDK Docker container.
+
+# Emscripten version to build: Should match the version that has been already released.
+# i.e.:  1.39.18
+version =
+alias =
+only_alias =
+
+image_name ?= emscripten/emsdk
+
+.TEST:
+ifndef version
+	$(error argument 'version' is not set. Please call `make version=SOME_VERSION ...`)
+endif
+
+build: Dockerfile .TEST
+	cd .. && docker build --progress=plain --network host --build-arg=EMSCRIPTEN_VERSION=${version} -t ${image_name}:${version} -f docker/$< .
+
+test: test_dockerimage.sh .TEST
+	# test as non-root
+	# test fallback env variables by overriding the entrypoint
+	docker run --rm -u `id -u`:`id -g` -w /emsdk/docker --net=host --entrypoint /bin/bash ${image_name}:${version} $<
+
+push: .TEST
+ifndef only_alias
+	docker push ${image_name}:${version}
+endif
+ifdef alias
+	docker tag ${image_name}:${version} ${image_name}:${alias}
+	docker push ${image_name}:${alias}
+endif