Fix "make tags": set locale to C to call sort

vim expects that the tags file is sorted using english collation, so it fails
if the locale is french for example. Use LC_ALL=C to force english sorting
order. Issue #27726.

Makefile.pre.in

@@ -1566,7 +1566,7 @@ tags::
 	ctags -w Include/*.h; \
 	for i in $(SRCDIRS); do ctags -w -a $$i/*.[ch]; \
 	done; \
-	sort -o tags tags
+	LC_ALL=C sort -o tags tags
 
 # Create a tags file for GNU Emacs
 TAGS::