prevent double quoting for $(datadir)

* mk/default.mk (MAKE_ORG_VERSION): Keep $(datadir) outside quotes,
  should already be shell-quoted.

Reported by Bernd Haug.

mk/default.mk

@@ -92,7 +92,7 @@ MAKE_ORG_INSTALL = $(BATCHL) \
 MAKE_ORG_VERSION = $(BATCHL) \
 	  --eval '(load "org-compat.el")' \
 	  --eval '(load "../mk/org-fixup.el")' \
-	  --eval '(org-make-org-version "$(ORGVERSION)" "$(GITVERSION)" "$(datadir)")'
+	  --eval '(org-make-org-version "$(ORGVERSION)" "$(GITVERSION)" "'$(datadir)'")'
 
 # How to byte-compile the whole source directory
 ELCDIR	= $(BATCHL) \