build: Add ENV container=oci

Since our stuff depends on this.

Author: cgwalters

Dockerfile

@@ -1,6 +1,8 @@
 # When rebasing to new Fedora, also update openshift/release:
 # https://github.com/openshift/release/tree/master/ci-operator/config/coreos/coreos-assembler/coreos-coreos-assembler-main.yaml
 FROM quay.io/fedora/fedora:40
+# Work around for https://bugzilla.redhat.com/show_bug.cgi?id=2278652
+ENV container=oci
 WORKDIR /root/containerbuild
 
 # Keep this Dockerfile idempotent for local development rebuild use cases.