Add multiarch builds

Author: mzazrivec

.tekton/cluster-api-provider-aws-mce-210-push.yaml

@@ -27,6 +27,9 @@ spec:
   - name: build-platforms
     value:
     - linux/x86_64
+    - linux/arm64
+    - linux/ppc64le
+    - linux/s390x
   - name: dockerfile
     value: stolostron/Dockerfile.stolostron
   - name: path-context