Hadrian should make use of -dynamic-too

Motivation

Hadrian doesn't make use of -dynamic-too at all right now, as spotted by @AndreasK. We definitely want to use it whenever possible, since for all flavours that build both the vanilla and dynamic ways (all but quickest?), this could allow us to build vanilla (static) and dynamic object files in for a module in a single command.

Proposal

Emit -dynamic-too when building Haskell modules when the current Flavour's libraryWays contains both vanilla and dynamic, and omit the need to build the object files the dynamic way. All of this only when platformSupportsSharedLibs holds.