Rework to stop using removed buildah feature

We can't rely on https://github.com/containers/buildah/issues/5952
anymore.

Signed-off-by: Colin Walters <walters@verbum.org>

Containerfile

@@ -1,7 +1,7 @@
 # This generates the default base image.
 
 # This is a local reference by default because we haven't shipped this image yet.
-FROM localhost/fedora-bootc:base as rootfs
+FROM localhost/fedora-bootc:base
 # Drop our package sets into /usr/share/doc, so that other things can parse it
 COPY packages*.txt /usr/share/doc/fedora-bootc/
 # Overlay our defaults
@@ -40,20 +40,3 @@ dnf clean all
 rm -vrf /var/log /var/cache /var/lib/dnf
 bootc container lint
 EORUN
-
-# This image just needs rpm-ostree in the end that has
-# https://github.com/coreos/rpm-ostree/issues/5221
-FROM registry.gitlab.com/fedora/bootc/base-images-dev/fedora-bootc-dev:rawhide as builder
-RUN --mount=type=bind,rw=true,src=.,dst=/buildcontext,bind-propagation=shared \
-    --mount=from=rootfs,dst=/rootfs <<EORUN
-set -xeuo pipefail
-rm /buildcontext/out.oci -rf
-rpm-ostree experimental compose build-chunked-oci --bootc --format-version=1 \
-           --rootfs=/rootfs --output /buildcontext/out.oci
-EORUN
-
-FROM oci:./out.oci
-# Need to reference builder here to force ordering. But since we have to run
-# something anyway, we might as well cleanup after ourselves.
-RUN --mount=type=bind,from=builder,src=.,target=/var/tmp \
-    --mount=type=bind,rw=true,src=.,dst=/buildcontext,bind-propagation=shared rm /buildcontext/out.oci -rf