Check to see if docker cache stays intact when run directly in workflows.

.github/workflows/docker_local_cache.yml

@@ -0,0 +1,48 @@
+name: Docker build (cache w/ docker)
+
+on:
+  workflow_dispatch:
+  push:
+    branches: [ "master", "main", "maint/*", "gha-docker-build" ]
+    tags: "*"
+  pull_request:
+    branches: [ "master", "main", "maint/*" ]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+  FORCE_COLOR: true
+
+jobs:
+  build-container:
+    runs-on: local
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v5
+        with:
+          fetch-depth: 200
+          fetch-tags: true
+
+      - name: Log into registry ${{ env.REGISTRY }}
+        if: github.event_name != 'pull_request'
+        run: |
+          echo "${{ secrets.GITHUB_TOKEN }}" | docker login ${{ env.REGISTRY }} -u ${{ github.actor }} --password-stdin
+
+      - name: Extract Docker metadata
+        id: meta
+        run: |
+          # Simple tag generation
+          TAGS="${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:main"
+          echo "tags=${TAGS}" >> $GITHUB_OUTPUT
+          echo "labels=" >> $GITHUB_OUTPUT
+
+      - name: Build and push Docker image
+        run: |
+          docker build -t ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:main .