CI: docs speedup by caching first stage (#29397)

* docs speedup

* fix tags on docs build

* build docs without build-push-action

.github/workflows/tools_tests.yaml

@@ -81,9 +81,11 @@ jobs:
         submodules: true
     - name: Build docker container
       run: |
-        DOCKER_BUILDKIT=1 docker build --pull --build-arg BUILDKIT_INLINE_CACHE=1 --cache-from $DOCKER_REGISTRY/openpilot-docs:latest -t $DOCKER_REGISTRY/openpilot-docs:latest -f docs/docker/Dockerfile .
+        DOCKER_BUILDKIT=1 docker build --pull --build-arg BUILDKIT_INLINE_CACHE=1 --cache-from $DOCKER_REGISTRY/openpilot-docs-base:latest -t $DOCKER_REGISTRY/openpilot-docs-base:latest -f docs/docker/Dockerfile --target openpilot-docs-base .
+        DOCKER_BUILDKIT=1 docker build --pull --build-arg BUILDKIT_INLINE_CACHE=1 --cache-from $DOCKER_REGISTRY/openpilot-docs-base:latest --cache-from $DOCKER_REGISTRY/openpilot-docs:latest -t $DOCKER_REGISTRY/openpilot-docs:latest -f docs/docker/Dockerfile .
     - name: Push docker container
       if: github.ref == 'refs/heads/master' && github.event_name != 'pull_request' && github.repository == 'commaai/openpilot'
       run: |
         $DOCKER_LOGIN
-        docker push $DOCKER_REGISTRY/openpilot-docs:latest
+        docker push $DOCKER_REGISTRY/openpilot-docs-base:latest
+        docker push $DOCKER_REGISTRY/openpilot-docs:latest

docs/docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM ghcr.io/commaai/openpilot-base:latest
+FROM ghcr.io/commaai/openpilot-base:latest as openpilot-docs-base
 
 ENV PYTHONUNBUFFERED 1