Support statically-linked GHC

[judah]

Currently hrepl assumes GHC is dynamically linked and that ghci will load dynamic libraries. Quoting tweag/rules_haskell#1210 (comment), there are two situations where this is relevant:

1. A static-mode GHC toolchain (e.g. on Windows) where Haskell libraries are only compiled to static archives. GHCi can load these, provided they are built with -fPIC (and -fexternal-dynamic-refs on Unix).
2. A C library dependency that only provides a pic_static_library. GHCi's loader can usually load these.