enable multi arch for push

Signed-off-by: Mangaal <angommeeteimangaal@gmail.com>

Author: Mangaal

.tekton/gitops-backend-push.yaml

@@ -26,6 +26,9 @@ spec:
   - name: build-platforms
     value:
     - linux/x86_64
+    - linux/arm64
+    - linux/ppc64le
+    - linux/s390x
   - name: dockerfile
     value: .konflux/Containerfile.plugin
   - name: hermetic