SF patch #524005 by Paul Eggert.

Use posixly correct sort args.

Bugfix candidate.
diff --git a/Makefile.pre.in b/Makefile.pre.in
index f964e41..5bed545 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -828,7 +828,7 @@
 	ctags -w -t Include/*.h; \
 	for i in $(SRCDIRS); do ctags -w -t -a $$i/*.[ch]; \
 	done; \
-	sort tags -o tags
+	sort -o tags tags
 
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