Separate Pretix ARM base build in it is own workflow

.github/workflows/build-base-pretix.yml

@@ -0,0 +1,45 @@
+name: Build base pretix image
+
+concurrency: ${{ inputs.version }}
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'The version of pretix to build. Example: v2024.10.0'
+        required: true
+        type: string
+
+jobs:
+  build:
+    name: Build
+    runs-on: [self-hosted]
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - name: Log in to the Container registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - uses: actions/checkout@v4
+        with:
+          repository: pretix/pretix
+          ref: ${{ inputs.version }}
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Build pretix base
+        uses: docker/build-push-action@v6
+        id: build-pretix-base
+        with:
+          context: .
+          builder: ${{ steps.buildx.outputs.name }}
+          provenance: false
+          push: true
+          tags: ghcr.io/pythonitalia/pycon/arm-pretix:${{ inputs.version }}
+          cache-from: type=local,src=/tmp/.buildx-cache
+          cache-to: type=local,dest=/tmp/.buildx-cache
+          platforms: linux/arm64