liquidhaskell.cabal: don't re-compile library modules for tests
liquidhaskell.cabal: don't re-compile library modules for tests

Link the library instead!

ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell