Add Docker caching to GitHub actions workflow

Add layer caching to speed up the CI builds. In addition, optimize the
Dockerfiles by moving all the dependency installations (which are
unlikely to change much) to the initial layers.

.github/workflows/build-and-test.yml

@@ -28,12 +28,24 @@ jobs:
         with:
           driver-opts: network=host
 
+      # Set up Docker caching. See
+      # https://github.com/docker/build-push-action/blob/master/docs/advanced/cache.md
+      - name: Cache Docker layers
+        uses: actions/cache@v2
+        with:
+          path: /tmp/.buildx-cache
+          key: ${{ runner.os }}-buildx-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-buildx-
+
       - name: Build the Chrome version of curl-impersonate
         uses: docker/build-push-action@v2
         with:
           push: true
           context: chrome/
           tags: localhost:5000/curl-impersonate/chrome
+          cache-from: type=local,src=/tmp/.buildx-cache
+          cache-to: type=local,dest=/tmp/.buildx-cache-new,mode=max
 
       - name: Build the Firefox version of curl-impersonate
         uses: docker/build-push-action@v2
@@ -41,6 +53,8 @@ jobs:
           push: true
           context: firefox/
           tags: localhost:5000/curl-impersonate/ff
+          cache-from: type=local,src=/tmp/.buildx-cache
+          cache-to: type=local,dest=/tmp/.buildx-cache-new,mode=max
 
       - name: Build the tests container
         uses: docker/build-push-action@v2
@@ -54,3 +68,11 @@ jobs:
 
       - name: Run the tests
         run: docker run --rm curl-impersonate-tests --log-cli-level DEBUG
+
+      # Temp fix
+      # https://github.com/docker/build-push-action/issues/252
+      # https://github.com/moby/buildkit/issues/1896
+      - name: Move cache
+        run: |
+          rm -rf /tmp/.buildx-cache
+          mv /tmp/.buildx-cache-new /tmp/.buildx-cache