ox-latex: Set inputenc option according to `org-export-coding-system'

* lisp/ox-latex.el (org-latex-guess-inputenc): Set inputenc option
  according to `org-export-coding-system'.

lisp/ox-latex.el

@@ -952,7 +952,7 @@ when specified inputenc option is \"AUTO\".
 Return the new header, as a string."
   (let* ((cs (or (ignore-errors
 		   (latexenc-coding-system-to-inputenc
-		    buffer-file-coding-system))
+		    (or org-export-coding-system buffer-file-coding-system)))
 		 "utf8")))
     (if (not cs) header
       ;; First translate if that is requested.