Refactor docker/Makefile to push images directly to registry

[straight-shoota]

As discussed in #389, exporting the docker images to disk and reimporting them in the next job is very expensive. It should be more efficient to push them directly from the builder job to the registry.

Successful workflow run: https://app.circleci.com/pipelines/github/crystal-lang/crystal/20041/workflows/bcae698e-c557-456d-ad93-b23cf4348786

[ysbaddaden]

The Makefile is becoming undecipherable. Wouldn't a stupid, POSIX compliant, Makefile with a few blunt targets and copy-pasted commands be much more readable and maintainable? We don't have many targets that we need any abstraction. Let's forget small steps, be blunt, and be done with it 📦

$ cd docker/
$ make VERSION=$(CRYSTAL_VERSION) TARBALLS=/tmp/workspace/build

.POSIX:
.PHONY:

TARBALLS = ./tarballs
BUILD_CONTEXT = ./build
PLATFORMS = linux/amd64,linux/arm64

VERSION = latest
TAG = crystal-lang/crystal:$(VERSION)

all: images smoke-test push

setup: .PHONY
  mkdir -p $(BUILD_CONTEXT)
  cp $(TARBALLS)/crystal-$(VERSION)-1-linux-x86_64.tar.gz $(BUILD_CONTEXT)/crystal-amd64.tar.gz
  cp $(TARBALLS)/crystal-$(VERSION)-1-linux-aarch64.tar.gz $(BUILD_CONTEXT)/crystal-arm64.tar.gz

images: alpine ubuntu 84codes

alpine: setup
  docker buildx build alpine.Dockerfile -t $(TAG)-alpine --target runtime --platform $(PLATFORMS) $(BUILD_CONTEXT)
  docker buildx build alpine.Dockerfile -t $(TAG)-alpine-build --target build --platform $(PLATFORMS) $(BUILD_CONTEXT)

ubuntu: setup
  docker buildx build ubuntu.Dockerfile -t $(TAG)-ubuntu --target runtime --platform $(PLATFORMS) $(BUILD_CONTEXT)
  docker buildx build ubuntu.Dockerfile -t $(TAG)-ubuntu-build --target build --platform $(PLATFORMS) $(BUILD_CONTEXT)

84codes: .PHONY
  docker buildx build --build-arg crystal_version=$(VERSION) -f alpine-84codes.Dockerfile --platform $(PLATFORMS) -t $(TAG)-alpine-84codes-build .
  docker buildx build --build-arg crystal_version=$(VERSION) -f ubuntu-84codes.Dockerfile --platform $(PLATFORMS) -t $(TAG)-ubuntu-84codes-build .

smoke-test: .PHONY
  docker run --rm -v $(PWD)/smoke.sh:/smoke.sh -e CRYSTAL_VERSION=$(VERSION) $(TAG)-alpine /smoke.sh $*
  docker run --rm -v $(PWD)/smoke.sh:/smoke.sh -e CRYSTAL_VERSION=$(VERSION) $(TAG)-ubuntu /smoke.sh $*

push: .PHONY
  docker push $(TAG)-alpine $(TAG)-alpine-build $(TAG)-alpine-84-codes-build
  docker push $(TAG)-ubuntu $(TAG)-ubuntu-build $(TAG)-ubuntu-84-codes-build

clean: .PHONY
  rm -rf $(BUILD_CONTEXT)

[straight-shoota]

I suppose we could expand the recipes to be less cryptic.
However, I do prefer individual recipes for each image with explicit prerequisites. When I need to build a specific image, I'd like to be able to do just that without having to build all image variants and provide all tarballs.