Windows runtime linker failure with icuuc

First, install mingw-w64-x86_64-icu (I'm using version 58.2-2):

$ pacman -S mingw-w64-x86_64-icu

Now take this file:

module Main where

import Data.Int
import Foreign
import Foreign.C.String
import Foreign.C.Types

type UErrorCode = CInt

u_ZERO_ERROR :: UErrorCode
u_ZERO_ERROR = 0

foreign import ccall "ucnv_open_58"
  c_ucnv_open :: CString -> Ptr UErrorCode -> IO (Ptr ())

foreign import ccall "ucnv_getMaxCharSize_58"
  c_ucnv_getMaxCharSize :: Ptr () -> IO Int8

main :: IO ()
main = with u_ZERO_ERROR $ \status -> do
  conv <- c_ucnv_open nullPtr status
  c_ucnv_getMaxCharSize conv >>= print

GHC is able to compile this successfully:

$ ghc -licuuc Bug2.hs
[1 of 1] Compiling Main             ( Bug2.hs, Bug2.o )
Linking Bug2.exe ...

$ ./Bug2.exe
1

But GHCi is unable to accomplish the same thing:

$ runghc -licuuc Bug2.hs
ghc.exe:  | C:\Users\RyanGlScott\Documents\Hacking\Haskell\Bug2.o: unknown symbol `ucnv_open_58'
Bug2.hs:

Phyx- and I discussed this briefly on IRC. He suspected that the fact that C:\Windows\System32 now contains its own copy of icuuc.dll is contributing to the issue.