Make it work with POSIX sort (POS arg)

All old sorts understand -k too.

usr.bin/lorder/lorder.sh

@@ -79,7 +79,7 @@ ${NM} -go $* | sed "
 
 # sort symbols and references on the first field (the symbol)
 # join on that field, and print out the file names.
-sort +1 $R -o $R
-sort +1 $S -o $S
+sort -k 2 $R -o $R
+sort -k 2 $S -o $S
 join -j 2 -o 1.1 2.1 $R $S
 rm -f $R $S