Update build-container.yml to build for arm64

Author: mwestphall

.github/workflows/build-container.yml

@@ -77,6 +77,7 @@ jobs:
       with:
         context: .
         push: true
+        platforms: linux/amd64,linux/arm64
         build-args: |
           IMAGE_BASE=${{ matrix.base.image }}
           BASE_YUM_REPO=${{ matrix.repo }}