misc,util-docker: Fix docker-build.yaml (#285)

https://github.com/gem5/gem5/actions/runs/6114221855 failure was due to
to running the actions inside our 22.04-all-dependencies container. This
container does not contain docker. We must therefore run this action
outside of the container. However, due to our policy of checking out the
code within this container, we must split this into two jobs and use the
artifact upload and download to get the resources we want.

.github/workflows/docker-build.yaml

@@ -3,21 +3,34 @@ name: Docker images build and push
 on:
   workflow_dispatch:
 jobs:
-  # This builds and pushes the docker image.
-  build-and-push:
+  obtain-dockerfiles:
     runs-on: [self-hosted, linux, x64, run]
-    permissions:
-      packages: write
-      contents: read
     container: gcr.io/gem5-test/ubuntu-22.04_all-dependencies:latest
 
     steps:
       - uses: actions/checkout@v3
-        name: Checkout the develop branch
         with:
-            # Scheduled workflows run on the default branch by default. We
-            # therefore need to explicitly checkout the develop branch.
-            ref: develop
+          # Scheduled workflows run on the default branch by default. We
+          # therefore need to explicitly checkout the develop branch.
+          ref: develop
+      - uses: actions/upload-artifact@v2
+        with:
+          name: dockerfiles
+          path: util/dockerfiles
+
+  # This builds and pushes the docker image.
+  build-and-push:
+    runs-on: [self-hosted, linux, x64, run]
+    needs: obtain-dockerfiles
+    permissions:
+      packages: write
+      contents: read
+
+    steps:
+      - uses: actions/download-artifact@v2
+        with:
+          name: dockerfiles
+          path: dockerfiles
 
       - uses: docker/setup-qemu-action@v2
         name: Setup QEMU
@@ -35,5 +48,5 @@ jobs:
       - name: Build and push with bake
         uses: docker/bake-action@v3
         with:
-          files: util/dockerfiles/docker-bake.hcl
+          files: dockerfiles/docker-bake.hcl
           push: true