Revert "remove unneeded function"

This reverts commit 12831962d7.

snamellit/common.scm

@@ -278,6 +278,21 @@
    (service home-mcron-service-type)
    ))
 
+;; add folders at the end of a PATH like string, removing duplicates but 
+;; keeping the order of first occurrence
+(define
+  (add-folders-to-path path folders)
+  (if
+   (null?  folders)
+   (string-join
+    (delete-duplicates
+     (string-split path #\:))
+    ":")
+   (add-folders-to-path
+    (string-append path ":"
+                   (car folders))
+    (cdr folders))))
+
 (define-public %snam-desktop-services
   (list
    (service home-dbus-service-type)