pack: Squashfs build expression refers to (guix store database) & co.

Fixes a regression introduced in
c45477d2a1.
Reported by Christopher Baines <mail@cbaines.net>.

* guix/scripts/pack.scm (not-config?, guile-sqlite3&co): New variables.
(self-contained-tarball)[not-config?]: Remove.
[build]: Use GUILE-SQLITE3&CO for 'with-extensions'.
(squashfs-image)[libgcrypt]: New variable.
[build]: Use 'source-module-closure', 'make-config.scm', and
'with-extensions'.
(docker-image)[not-config?]: Remove.

guix/scripts/pack.scm

@@ -88,6 +88,19 @@ found."
             %compressors)
       (leave (G_ "~a: compressor not found~%") name)))
 
+(define not-config?
+  ;; Select (guix …) and (gnu …) modules, except (guix config).
+  (match-lambda
+    (('guix 'config) #f)
+    (('guix _ ...) #t)
+    (('gnu _ ...) #t)
+    (_ #f)))
+
+(define guile-sqlite3&co
+  ;; Guile-SQLite3 and its propagated inputs.
+  (cons guile-sqlite3
+        (package-transitive-propagated-inputs guile-sqlite3)))
+
 (define* (self-contained-tarball name profile
                                  #:key target
                                  deduplicate?
@@ -102,13 +115,6 @@ with a properly initialized store database.
 
 SYMLINKS must be a list of (SOURCE -> TARGET) tuples denoting symlinks to be
 added to the pack."
-  (define not-config?
-    (match-lambda
-      (('guix 'config) #f)
-      (('guix _ ...) #t)
-      (('gnu _ ...) #t)
-      (_ #f)))
-
   (define libgcrypt
     (module-ref (resolve-interface '(gnu packages gnupg))
                 'libgcrypt))
@@ -128,9 +134,7 @@ added to the pack."
                                   (guix build store-copy)
                                   (gnu build install))
                                 #:select? not-config?))
-      (with-extensions (cons guile-sqlite3
-                             (package-transitive-propagated-inputs
-                              guile-sqlite3))
+      (with-extensions guile-sqlite3&co
         #~(begin
             (use-modules (guix build utils)
                          ((guix build union) #:select (relative-file-name))
@@ -248,10 +252,22 @@ points for virtual file systems (like procfs), and optional symlinks.
 
 SYMLINKS must be a list of (SOURCE -> TARGET) tuples denoting symlinks to be
 added to the pack."
+  (define libgcrypt
+    ;; XXX: Not strictly needed, but pulled by (guix store database).
+    (module-ref (resolve-interface '(gnu packages gnupg))
+                'libgcrypt))
+
+
   (define build
-    (with-imported-modules '((guix build utils)
+    (with-imported-modules `(((guix config)
+                              => ,(make-config.scm
+                                   #:libgcrypt libgcrypt))
+                             ,@(source-module-closure
+                                '((guix build utils)
                                   (guix build store-copy)
                                   (gnu build install))
+                                #:select? not-config?))
+      (with-extensions guile-sqlite3&co
         #~(begin
             (use-modules (guix build utils)
                          (gnu build install)
@@ -312,7 +328,7 @@ added to the pack."
                      ;; Create empty mount points.
                      "-p" "/proc d 555 0 0"
                      "-p" "/sys d 555 0 0"
-                   "-p" "/dev d 555 0 0")))))
+                     "-p" "/dev d 555 0 0"))))))
 
   (gexp->derivation (string-append name
                                    (compressor-extension compressor)
@@ -332,14 +348,6 @@ image is a tarball conforming to the Docker Image Specification, compressed
 with COMPRESSOR.  It can be passed to 'docker load'.  If TARGET is true, it
 must a be a GNU triplet and it is used to derive the architecture metadata in
 the image."
-  ;; FIXME: Honor LOCALSTATEDIR?.
-  (define not-config?
-    (match-lambda
-      (('guix 'config) #f)
-      (('guix rest ...) #t)
-      (('gnu rest ...) #t)
-      (rest #f)))
-
   (define defmod 'define-module)                  ;trick Geiser
 
   (define config