packaging: Update infrastructure

The Makefile.dist-packaging lives canonically in rpm-ostree/ for now,
it's my latest hack to automate git -> (s)rpm.

Update the spec.in from current Fedora.

packaging/rpmbuild-cwd

@@ -0,0 +1,11 @@
+#!/bin/sh
+# rpmbuild-cwd:
+# Run "rpmbuild", defining all RPM variables to use the current directory.
+# This matches Fedora's system.
+#
+# Licensed under the new-BSD license (http://www.opensource.org/licenses/bsd-license.php)
+# Copyright (C) 2010 Red Hat, Inc.
+# Written by Colin Walters <walters@verbum.org>
+
+pwd=$(pwd)
+exec rpmbuild --define "_sourcedir ${pwd}" --define "_specdir ${pwd}" --define "_builddir ${pwd}" --define "_srcrpmdir ${pwd}" --define "_rpmdir ${pwd}" --define "_buildrootdir ${pwd}/.build" "$@"