Support builds that doesn't use cabal for libs and rts

This makes it possible to build idrises that don't depend on cabal to store the lib files. It is enabled by -f freestanding and takes the dir where the files will be in IDRIS_INSTALL_DIR (it can be either relative to the executable or an absolute path). It does nothing to actually place the files there (because this is presumably a prelude to building an installer or linux/bsd package)