isDllName: use Opt_ExternalDynamicRefs, not WayDyn
isDllName: use Opt_ExternalDynamicRefs, not WayDyn

This should have been part of D4477, but got missed.

sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc