ci: remove dangling packages from CI workers

.github/workflows/test-tools.yml

@@ -4,26 +4,47 @@ on:
     branches:
       - main
       - develop
-    paths:
-      - Dockerfile
   pull_request:
     branches:
       - main
       - develop
-    paths:
-      - Dockerfile
 
 jobs:
   build-and-test:
     runs-on: ubuntu-latest
     steps:
+      # This step takes ages (~4-5 min) but frees around 20 additional gigabytes
+      # that are quite useful when installing and running everything.
+      - name: Free up some disk space
+        uses: jlumbroso/free-disk-space@main
+        with:
+          tool-cache: false
+          android: true
+          dotnet: true
+          haskell: true
+          large-packages: false
+          swap-storage: false
+          docker-images: false
+
       - name: Checkout
         uses: actions/checkout@v4
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
-      - name: Build container using Make
-        run: make build
-        env:
-          DOCKER_BUILDKIT: 1
+      - name: Load .env file
+        id: dotenv
+        uses: xom9ikk/dotenv@v2
+
+      - name: Build container
+        uses: docker/build-push-action@v6
+        with:
+          push: false
+          context: .
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+          tags: theredguild/container-sec-tools:latest
+          build-args: ${{ steps.dotenv.outputs.vars }}
+
+      - name: Check disk space
+        run: df -h