Fix arm64 image builds in github actions

Add the 'platforms' option to arm64 image builds. Otherwise, builds are
still in amd64 containers.

Signed-off-by: Blaine Gardner <blaine.gardner@redhat.com>

.github/workflows/image-build.yml

@@ -54,3 +54,4 @@ jobs:
           push: false
           tags: ghcr.io/${{ github.repository }}:latest-arm64
           file: Dockerfile.arm64
+          platforms: linux/arm64

.github/workflows/image-push-master.yml

@@ -1,5 +1,5 @@
 name: Image push for master
-on: 
+on:
   push:
     branches:
       - master
@@ -59,3 +59,4 @@ jobs:
           push: true
           tags: ghcr.io/${{ github.repository }}:latest-ocp
           file: Dockerfile.openshift
+          platforms: linux/arm64

.github/workflows/image-push-release.yml

@@ -1,5 +1,5 @@
 name: Image push release
-on: 
+on:
   push:
     tags:
       - v*
@@ -75,3 +75,4 @@ jobs:
           tags: |
             ${{ steps.docker_meta.outputs.tags }}-arm64
           file: Dockerfile
+          platforms: linux/arm64