pack: Import (guix store database) only when '--localstatedir' is passed.

This is another way to address <https://bugs.gnu.org/32184>, which was
previously addressed in commit 19c924af4f.

* gnu/build/install.scm (register-closure): Move to...
* gnu/build/vm.scm (register-closure): ... here.  New procedure.
* guix/scripts/pack.scm (self-contained-tarball)[build]: Remove
now unneeded 'with-extensions' form and custom (guix config) module.
* tests/guix-pack.sh: Revert the strategy from
commit 19c924af4f.
* tests/pack.scm ("self-contained-tarball"): Likewise.

gnu/build/install.scm

@@ -18,7 +18,6 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (gnu build install)
-  #:use-module (guix store database)
   #:use-module (guix build utils)
   #:use-module (guix build store-copy)
   #:use-module (srfi srfi-26)
@@ -141,23 +140,6 @@ includes /etc, /var, /run, /bin/sh, etc., and all the symlinks to SYSTEM."
                 (try))
               (apply throw args)))))))
 
-(define* (register-closure prefix closure
-                           #:key
-                           (deduplicate? #t) (reset-timestamps? #t)
-                           (schema (sql-schema)))
-  "Register CLOSURE in PREFIX, where PREFIX is the directory name of the
-target store and CLOSURE is the name of a file containing a reference graph as
-produced by #:references-graphs..  As a side effect, if RESET-TIMESTAMPS? is
-true, reset timestamps on store files and, if DEDUPLICATE? is true,
-deduplicates files common to CLOSURE and the rest of PREFIX."
-  (let ((items (call-with-input-file closure read-reference-graph)))
-    (register-items items
-                    #:prefix prefix
-                    #:deduplicate? deduplicate?
-                    #:reset-timestamps? reset-timestamps?
-                    #:registration-time %epoch
-                    #:schema schema)))
-
 (define* (populate-single-profile-directory directory
                                             #:key profile closure
                                             (profile-name "guix-profile")

gnu/build/vm.scm

@@ -25,7 +25,7 @@
   #:use-module (guix build utils)
   #:use-module (guix build store-copy)
   #:use-module (guix build syscalls)
-  #:use-module ((guix store database) #:select (reset-timestamps))
+  #:use-module (guix store database)
   #:use-module (gnu build linux-boot)
   #:use-module (gnu build install)
   #:use-module (gnu system uuid)
@@ -191,6 +191,23 @@ the #:references-graphs parameter of 'derivation'."
           (mkdir output)
           (copy-recursively "xchg" output)))))
 
+(define* (register-closure prefix closure
+                           #:key
+                           (deduplicate? #t) (reset-timestamps? #t)
+                           (schema (sql-schema)))
+  "Register CLOSURE in PREFIX, where PREFIX is the directory name of the
+target store and CLOSURE is the name of a file containing a reference graph as
+produced by #:references-graphs..  As a side effect, if RESET-TIMESTAMPS? is
+true, reset timestamps on store files and, if DEDUPLICATE? is true,
+deduplicates files common to CLOSURE and the rest of PREFIX."
+  (let ((items (call-with-input-file closure read-reference-graph)))
+    (register-items items
+                    #:prefix prefix
+                    #:deduplicate? deduplicate?
+                    #:reset-timestamps? reset-timestamps?
+                    #:registration-time %epoch
+                    #:schema schema)))
+
 
 ;;;
 ;;; Partitions.