Remove unnecessary use of -DGENERICS flag
Remove unnecessary use of -DGENERICS flag

This flag was only needed for old versions of binary, and now that we've
upgraded to binary-0.8.4.1, it is no longer necessary.

ezyang/ghc,ezyang/ghc,ezyang/ghc,ezyang/ghc,sdiehl/ghc,ezyang/ghc,sdiehl/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,ezyang/ghc,sdiehl/ghc,sdiehl/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,ezyang/ghc,sdiehl/ghc