feat: add GitHub Actions workflow for publishing Build Tools Docker image

Signed-off-by: Matthieu MOREL <matthieu.morel35@gmail.com>

Author: mmorel-35

.github/workflows/publish-build-tools.yml

@@ -0,0 +1,76 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: Publish Build Tools Docker Image
+
+on:
+  workflow_dispatch:
+    inputs:
+      ubuntu_version:
+        description: 'Ubuntu version for base image'
+        required: true
+      bazel_version:
+        description: 'Bazel version to build'
+        required: true
+      platforms:
+        description: 'Target platforms (comma-separated)'
+        required: false
+        default: 'linux/s390x'
+      draft:
+        description: 'Draft mode (true: build only, false: build and push)'
+        type: boolean
+        required: false
+        default: true
+
+jobs:
+  publish:
+    runs-on: ubuntu-24.04-16core
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Generate tag
+      id: tag
+      run: |
+        TAG="ubuntu-${{ github.event.inputs.ubuntu_version }}-bazel-${{ github.event.inputs.bazel_version }}"
+        echo "tag=$TAG" >> $GITHUB_OUTPUT
+
+    - name: Login to GitHub Container Registry
+      if: ${{ !github.event.inputs.draft }}
+      uses: docker/login-action@v3
+      with:
+        registry: ghcr.io
+        username: ${{ github.actor }}
+        password: ${{ secrets.GITHUB_TOKEN }}
+
+    - name: Set up Docker Buildx
+      uses: docker/setup-buildx-action@v3
+
+    - name: Build and Push Docker Image
+      uses: docker/build-push-action@v6
+      with:
+        context: .
+        file: bazel/external/Dockerfile.bazel
+        platforms: ${{ github.event.inputs.platforms }}
+        tags: ghcr.io/proxy-wasm/build-tools:${{ steps.tag.outputs.tag }}
+        build-args: |
+          UBUNTU_VERSION=${{ github.event.inputs.ubuntu_version }}
+          BAZEL_VERSION=${{ github.event.inputs.bazel_version }}
+        push: ${{ !github.event.inputs.draft }}
+        load: ${{ github.event.inputs.draft }}
+        cache-from: type=gha,scope=build-tools-${{ steps.tag.outputs.tag }}
+        cache-to: type=gha,mode=max,scope=build-tools-${{ steps.tag.outputs.tag }}