Avoid clobbering RPMDB in final container

Installing the RPMs in an alternate root and then copying the contents
of that root to the final container rootfs overwrites the RPM database
in the latter with the one from the former.  This isn't necessarily
a problem per se, but it makes troubleshooting difficult.  To avoid
this, we can install the RPMs directly in the final filesystem, which
mutates the RPMDB without overwriting it.

Containerfile

@@ -9,7 +9,7 @@ RUN --mount=type=cache,target=/var/cache \
 RUN --mount=type=cache,target=/var/cache \
 	dnf install -y \
 		--downloadonly \
-		--downloaddir=/var/cache/rpms \
+		--downloaddir=/rpms \
 		--setopt=install_weak_deps=0 \
 		collectd \
 		collectd-chrony \
@@ -19,21 +19,22 @@ RUN --mount=type=cache,target=/var/cache \
 		collectd-write_prometheus \
 	&& :
 
-RUN --mount=type=cache,target=/var/cache \
-	rpm -ivh -f --nodeps --root=/sysroot \
-		/var/cache/rpms/collectd*.rpm \
-		/var/cache/rpms/lm_sensors-libs-*.rpm \
-		/var/cache/rpms/libmicrohttpd-*.rpm \
-		/var/cache/rpms/libmnl-*.rpm \
-		/var/cache/rpms/protobuf-c-*.rpm \
-	&& cd /sysroot \
-	&& rpm2cpio /var/cache/rpms/nut-client-*.rpm \
-		| cpio -i './usr/lib*/libupsclient.so.6*' \
-	&& :
-
 
 FROM registry.fedoraproject.org/fedora-minimal:40
 
-COPY --from=build /sysroot /
+RUN --mount=type=cache,target=/var/cache \
+	--mount=type=bind,from=build,source=/rpms,target=/rpms \
+	microdnf install -y \
+		--setopt=install_weak_deps=0 \
+		cpio \
+	&& rpm -ivh -f --nodeps \
+		/rpms/collectd*.rpm \
+		/rpms/lm_sensors-libs-*.rpm \
+		/rpms/libmicrohttpd-*.rpm \
+		/rpms/libmnl-*.rpm \
+		/rpms/protobuf-c-*.rpm \
+	&& rpm2cpio /rpms/nut-client-*.rpm \
+		| cpio -i './usr/lib*/libupsclient.so.6*' \
+	&& :
 
 ENTRYPOINT ["/usr/sbin/collectd", "-f"]