lisp/ob-tangle.el: Add variable declaration

This completes commit 0b4e357d6.

lisp/ob-tangle.el

@@ -43,6 +43,7 @@
 (declare-function org-in-commented-heading-p "org" (&optional no-inheritance))
 (declare-function org-in-archived-heading-p "org" (&optional no-inheritance))
 (declare-function outline-previous-heading "outline" ())
+(defvar org-id-link-to-org-use-id nil) ; Dynamically scoped
 
 (defcustom org-babel-tangle-lang-exts
   '(("emacs-lisp" . "el")