tests: Import (guix build utils) in the marionette.

* gnu/tests/install.scm (%minimal-os)[marionette-configuration](imported-modules):
Add (guix build utils).
* gnu/tests/base.scm (run-basic-test)["skeletons in home directories"]:
Use (guix build utils) explicitly.

gnu/tests/base.scm

@@ -223,8 +223,8 @@ info --version")
                                   (operating-system-user-accounts os))))
               (marionette-eval
                `(begin
-                  (use-modules (srfi srfi-1) (ice-9 ftw)
-                               (ice-9 match))
+                  (use-modules (guix build utils) (srfi srfi-1)
+                               (ice-9 ftw) (ice-9 match))
 
                   (every (match-lambda
                            ((user home)

gnu/tests/install.scm

@@ -79,6 +79,7 @@
     (services (cons (service marionette-service-type
                              (marionette-configuration
                               (imported-modules '((gnu services herd)
+                                                  (guix build utils)
                                                   (guix combinators)))))
                     %base-services))))