CI: create Docker container containing compiled tools

Currently each Kernel compilation takes about 30 minutes of which 20
minutes are used to compile our tools. While the toolchain is downloaded
and instantly ready the tools are missing.

This commit starts uploading a Docker container including compiled tools
which are ready to use. It is automatically updated whenever any tools
are changed.

Signed-off-by: Paul Spooren <mail@aparcar.org>
Co-Developed-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
(cherry picked from commit 25b65f548dfd93cae87781276bfff9a27cd3ebd4)

.github/workflows/Dockerfile.tools

@@ -0,0 +1,3 @@
+FROM registry.gitlab.com/openwrt/buildbot/buildworker-3.4.1
+
+COPY --chown=buildbot:buildbot tools.tar /tools.tar

.github/workflows/tools.yml

@@ -5,12 +5,17 @@ on:
     paths:
       - 'tools/**'
       - '.github/workflows/tools.yml'
+  push:
+    paths:
+      - 'tools/**'
+      - '.github/workflows/tools.yml'
 
 permissions:
   contents: read
 
 jobs:
   build-macos-latest:
+    if: github.event_name != 'push'
     runs-on: macos-latest
 
     steps:
@@ -105,6 +110,15 @@ jobs:
         run: |
           chown -R buildbot:buildbot openwrt
 
+      - name: Set AUTOREMOVE config for tools container
+        if: github.event_name == 'push'
+        shell: su buildbot -c "sh -e {0}"
+        working-directory: openwrt
+        run: |
+          touch .config
+          echo CONFIG_DEVEL=y >> .config
+          echo CONFIG_AUTOREMOVE=y >> .config
+
       - name: Make prereq
         shell: su buildbot -c "sh -e {0}"
         working-directory: openwrt
@@ -128,3 +142,53 @@ jobs:
         with:
           name: linux-buildbot-config
           path: openwrt/.config
+
+      - name: Archive prebuilt tools
+        if: github.event_name == 'push'
+        shell: su buildbot -c "sh -e {0}"
+        working-directory: openwrt
+        run: tar --mtime=now -cf tools.tar staging_dir/host build_dir/host dl
+
+      - name: Upload prebuilt tools
+        if: github.event_name == 'push'
+        uses: actions/upload-artifact@v2
+        with:
+          name: linux-buildbot-prebuilt-tools
+          path: openwrt/tools.tar
+          retention-days: 1
+
+  push-tools-container:
+    needs: build-linux-buildbot
+    runs-on: ubuntu-latest
+    if: github.event_name == 'push'
+
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          path: 'openwrt'
+
+      - name: Download prebuilt tools from build job
+        uses: actions/download-artifact@v2
+        with:
+          name: linux-buildbot-prebuilt-tools
+          path: openwrt
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v2
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v3
+        with:
+          context: openwrt
+          push: true
+          tags: ghcr.io/${{ github.repository_owner }}/tools:latest
+          file: openwrt/.github/workflows/Dockerfile.tools