[hail] avoid != in Makefile (#6891)
[hail] avoid != in Makefile (#6891)

I like the != syntax but it is not supported by the Make shipped
with recent OS X versions, so I think we should avoid it.
cseed/hail,cseed/hail,hail-is/hail,hail-is/hail,hail-is/hail,danking/hail,cseed/hail,cseed/hail,cseed/hail,cseed/hail,cseed/hail,cseed/hail,danking/hail,hail-is/hail,hail-is/hail,hail-is/hail,danking/hail,danking/hail,danking/hail,danking/hail,danking/hail,hail-is/hail,danking/hail,hail-is/hail