Add usr.bin/ar to the list of cross tools.  Before, when we had gnu ar, it was built in the gnu/usr.bin/binutils tree.  Now it isn't.
Add usr.bin/ar to the list of cross tools.  Before, when we had gnu
ar, it was built in the gnu/usr.bin/binutils tree.  Now it isn't.

Submitted by:	John Hein

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