Use docker/login-action instead of command-line for ghcr too

.github/workflows/build_multiarch.yml

@@ -44,6 +44,12 @@ jobs:
         username: ${{ secrets.DOCKER_USER }}
         password: ${{ secrets.DOCKER_PASS }}
 
+    - uses: docker/login-action@v3
+      with:
+        registry: ghcr.io
+        username: ${{ secrets.GHCR_USER }}
+        password: ${{ secrets.GHCR_ACCESS_TOKEN }}
+
     - run: |
         if [ "${{ env.dev_suffix }}" = "-dev" ]; then
           echo "target=development" >> $GITHUB_ENV
@@ -99,7 +105,6 @@ jobs:
     - name: Push docker image to ghcr.io/ruby
       if: "${{ env.push_tags }}"
       run: |-
-        echo $GHCR_ACCESS_TOKEN | docker login ghcr.io -u $GHCR_USER --password-stdin
         push_tags="${{ env.push_tags }}"
         for tag in $push_tags; do
           docker tag rubylang/ruby:$tag ghcr.io/ruby/ruby:$tag