build: Add missing 'make-binary-tarball.scm' script.

This script is used by the target added in 9d3fb6c.

* build-aux/make-binary-tarball.scm: New file.
* Makefile.am (EXTRA_DIST): Add it.

Makefile.am

@@ -257,6 +257,7 @@ EXTRA_DIST =						\
   build-aux/check-final-inputs-self-contained.scm	\
   build-aux/download.scm				\
   build-aux/list-packages.scm				\
+  build-aux/make-binary-tarball.scm			\
   srfi/srfi-37.scm.in					\
   srfi/srfi-64.scm					\
   srfi/srfi-64.upstream.scm				\

build-aux/make-binary-tarball.scm

@@ -0,0 +1,50 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2015 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+
+;;;
+;;; Build a self-contained tarball containing binaries for Guix and its
+;;; dependencies.
+;;;
+
+(use-modules (guix)
+             (guix ui)
+             (gnu system install)
+             (ice-9 match))
+
+(define show-what-to-build*
+  (store-lift show-what-to-build))
+
+(define copy-file*
+  (lift2 copy-file %store-monad))
+
+(define rename-file*
+  (lift2 rename-file %store-monad))
+
+(match (command-line)
+  ((_ system file)
+   (with-store store
+     (run-with-store store
+       (mlet %store-monad ((tarball (self-contained-tarball)))
+         (mbegin %store-monad
+           (show-what-to-build* (list tarball))
+           (built-derivations (list tarball))
+           (copy-file* (derivation->output-path tarball)
+                       (string-append file ".part"))
+           (rename-file* (string-append file ".part") file)))
+       #:system system))))