builder: New container image

This will be the container image buildroot.

builder/Dockerfile

@@ -0,0 +1,7 @@
+# This image contains the baseline tools to build bootable base images.
+FROM quay.io/centos/centos:stream9
+WORKDIR /src
+COPY . .
+RUN ./build.sh && cd / && rm /src -rf
+WORKDIR /
+

builder/build.sh

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+#!/bin/bash
+set -xeuo pipefail
+
+pkginstall() {
+    dnf -y install "$@"
+}
+
+pkginstall dnf-utils
+dnf config-manager --set-enabled crb
+pkginstall epel-release epel-next-release
+# The repo files reference GPG keys
+pkginstall distribution-gpg-keys
+# rpm-ostree for builds, and need skopeo to do the container backend
+pkginstall rpm-ostree skopeo
+# For derived container builds
+pkginstall buildah
+# And a rust toolchain
+pkginstall cargo openssl-devel
+
+# Build tools
+pkginstall selinux-policy-targeted osbuild crypto-policies-scripts sudo