profiles: Move build code to (guix build profiles).

* guix/build/profiles.scm: New file.
* Makefile.am (MODULES): Add it.
* guix/profiles.scm (profile-derivation)[builder]: Call out to
  'build-profile'.
  Add (guix build profiles) to the #:modules argument.

Makefile.am

@@ -79,6 +79,7 @@ MODULES =					\
   guix/build/store-copy.scm			\
   guix/build/utils.scm				\
   guix/build/union.scm				\
+  guix/build/profiles.scm			\
   guix/build/pull.scm				\
   guix/build/rpath.scm				\
   guix/build/cvs.scm				\

guix/build/profiles.scm

@@ -0,0 +1,41 @@
+;;; 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/>.
+
+(define-module (guix build profiles)
+  #:use-module (guix build union)
+  #:use-module (ice-9 pretty-print)
+  #:export (build-profile))
+
+;;; Commentary:
+;;;
+;;; Build a user profile (essentially the union of all the installed packages)
+;;; with its associated meta-data.
+;;;
+;;; Code:
+
+(define* (build-profile output inputs
+                        #:key manifest)
+  "Build a user profile from INPUTS in directory OUTPUT.  Write MANIFEST, an
+sexp, to OUTPUT/manifest."
+  (union-build output inputs
+               #:log-port (%make-void-port "w"))
+  (call-with-output-file (string-append output "/manifest")
+    (lambda (p)
+      (pretty-print manifest p))))
+
+;;; profile.scm ends here

guix/profiles.scm

@@ -598,20 +598,17 @@ (define inputs
 
     (define builder
       #~(begin
-          (use-modules (ice-9 pretty-print)
+          (use-modules (guix build profiles))
-                       (guix build union))
 
           (setvbuf (current-output-port) _IOLBF)
           (setvbuf (current-error-port) _IOLBF)
 
-          (union-build #$output '#$inputs
+          (build-profile #$output '#$inputs
-                       #:log-port (%make-void-port "w"))
+                         #:manifest '#$(manifest->gexp manifest))))
-          (call-with-output-file (string-append #$output "/manifest")
-            (lambda (p)
-              (pretty-print '#$(manifest->gexp manifest) p)))))
 
     (gexp->derivation "profile" builder
-                      #:modules '((guix build union))
+                      #:modules '((guix build union)
+                                  (guix build profiles))
                       #:local-build? #t)))
 
 (define (profile-regexp profile)