Producing FFI static binaries

Hi, thanks for your work on this!

I have a question regarding to the production of FFI binaries on Haskell using nix. Right now I'm trying to compile this project, https://github.com/treble-ai/duckling-ffi, which intends to produce a C-compliant static library. Until now, Nix is able to build the library and produces a static binary `libHSduckling-ffi-0.1.0.0-28aDIsnrQtXFlJL0Bi0HJ4.a`. However, when I inspect that binary using `nm`, I find that several Haskell runtime symbols are undefined, such as `base_GHCziForeign_zdwpeekCString_closure`, or `rts_getPtr`, which prevent the output library to be useful. Is there any way to produce a full, static binary using static-haskell-nix? Sorry for my lack of background, as I don't have any previous haskell/nix experience.