pack: Create /tmp in Apptainer images.

Related to <https://bugs.gnu.org/37161> and
<https://git.savannah.gnu.org/cgit/guix.git/commit/?id=7979a287f8eb84cbbfa44629951572408939a756>.

* guix/scripts/pack.scm (squashfs-image)[build]: Add /tmp to the set of
directories created.
* tests/pack.scm ("squashfs-image + localstatedir"): Check for /tmp.

Change-Id: I576aaa6ba8cb8478acf4c3144d492ae5caf411ca
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

guix/scripts/pack.scm

@@ -493,7 +493,8 @@ added to the pack."
                "-p" "/proc d 555 0 0"
                "-p" "/sys d 555 0 0"
                "-p" "/dev d 555 0 0"
-               "-p" "/home d 555 0 0"))
+               "-p" "/home d 555 0 0"
+               "-p" "/tmp d 555 0 0"))
 
             (when database
               ;; Initialize /var/guix.

tests/pack.scm

@@ -328,6 +328,7 @@
                            (when (and (file-exists? (string-append bin
                                                                    "/guile"))
                                       (file-exists? "var/guix/db/db.sqlite")
+                                      (file-is-directory? "tmp")
                                       (string=? (string-append #$%bootstrap-guile "/bin")
                                                 (pk 'binlink (readlink bin)))