Try adding a build cache that uses githubs package repo as a cache

Inspired by https://dev.to/dtinth/caching-docker-builds-in-github-actions-which-approach-is-the-fastest-a-research-18ei

.github/workflows/ci-workflow.yml

@@ -24,7 +24,18 @@ jobs:
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
       - uses: actions/checkout@v2
+      - name: Prepare docker build cache
+        run:
+          echo ${{ secrets.GITHUB_TOKEN }} | docker login docker.pkg.github.com -u $GITHUB_ACTOR --password-stdin
+          docker pull docker.pkg.github.com/$GITHUB_REPOSITORY/build-cache || true
+          export DOCKER_BUILD_OPTS="--cache-from=docker.pkg.github.com/$GITHUB_REPOSITORY/build-cache"
 
       # Run the make script
       - name: Make build
         run: make build
+
+      # Cache build outputs
+      - name: Save docker build cache
+        run:
+          docker tag netty-incubator-buffer:build docker.pkg.github.com/$GITHUB_REPOSITORY/build-cache
+          docker push docker.pkg.github.com/$GITHUB_REPOSITORY/build-cache || true

Makefile

@@ -2,7 +2,7 @@
 .DEFAULT_GOAL := build
 
 image:
-	docker build --tag netty-incubator-buffer:build .
+	docker build $(DOCKER_BUILD_OPTS) --tag netty-incubator-buffer:build .
 
 test: image
 	docker run --rm --name build-container netty-incubator-buffer:build