import: cpan: Sort inputs.

* guix/import/cpan.scm (cpan-module->sexp)[convert-inputs]: Sort returned list
  of inputs.

guix/import/cpan.scm

@@ -141,6 +141,7 @@ META."
       (#f
        '())
       ((inputs ...)
+       (sort
         (delete-duplicates
          ;; Listed dependencies may include core modules.  Filter those out.
          (filter-map (match-lambda
@@ -151,7 +152,11 @@ META."
                             (let ((name (guix-name (module->dist-name module))))
                               (list name
                                     (list 'unquote (string->symbol name)))))))
-                    inputs)))))
+                     inputs))
+        (lambda args
+          (match args
+            (((a _ ...) (b _ ...))
+             (string<? a b))))))))
 
   (define (maybe-inputs guix-name inputs)
     (match inputs