pass -B flag to help gcc find libraries on Windows

Distribution/Simple/GHC.hs

@@ -101,7 +101,7 @@ import Distribution.Simple.Program
          , rawSystemProgramStdout, rawSystemProgramStdoutConf, requireProgram
          , userMaybeSpecifyPath, programPath, lookupProgram, updateProgram
          , ghcProgram, ghcPkgProgram, arProgram, ranlibProgram, ldProgram
-         , gccProgram, stripProgram )
+         , gccProgram, stripProgram, userSpecifyArgs )
 import Distribution.Simple.Compiler
          ( CompilerFlavor(..), CompilerId(..), Compiler(..), compilerVersion
          , OptimisationLevel(..), PackageDB(..), Flag, extensionsToFlags )
@@ -155,12 +155,13 @@ configure verbosity hcPath hcPkgPath conf = do
     ++ programPath ghcPkgProg ++ " is version " ++ display ghcPkgVersion
 
   -- finding ghc's local gcc and ld is a bit tricky as it's not on the path:
-  let (gccProgram', ldProgram') = case buildOS of
+  let compilerDir = takeDirectory (programPath ghcProg)
+      baseDir     = takeDirectory compilerDir
+      libDir      = baseDir </> "gcc-lib"
+      (gccProgram', ldProgram') = case buildOS of
         Windows ->
-          let compilerDir  = takeDirectory (programPath ghcProg)
-              baseDir      = takeDirectory compilerDir
-              binInstallCc = baseDir </> "gcc.exe"
-              binInstallLd = baseDir </> "gcc-lib" </> "ld.exe"
+          let binInstallCc = baseDir </> "gcc.exe"
+              binInstallLd = libDir </> "ld.exe"
            in (gccProgram {
                   programFindLocation = \_ -> return (Just binInstallCc)
                 }
@@ -170,8 +171,11 @@ configure verbosity hcPath hcPkgPath conf = do
         _ -> (gccProgram, ldProgram)
 
   (_, conf''') <- requireProgram verbosity gccProgram' AnyVersion conf''
+  let conf'''' =  userSpecifyArgs "hsc2hs" ["--cflag=-B" ++ libDir, "--lflag=-B" ++ libDir]
+                                  conf'''
+
   -- we need to find out if ld supports the -x flag
-  (ldProg, conf'''') <- requireProgram verbosity ldProgram' AnyVersion conf'''
+  (ldProg, conf''''') <- requireProgram verbosity ldProgram' AnyVersion conf''''
   tempDir <- getTemporaryDirectory
   ldx <- withTempFile tempDir ".c" $ \testcfile testchnd ->
          withTempFile tempDir ".o" $ \testofile testohnd -> do
@@ -187,10 +191,10 @@ configure verbosity hcPath hcPkgPath conf = do
                return True
              `catchIO`   (\_ -> return False)
              `catchExit` (\_ -> return False)
-  let conf''''' = updateProgram ldProg {
+  let conf'''''' = updateProgram ldProg {
                   programArgs = if ldx then ["-x"] else []
-                } conf''''
-  -- Yeah yeah, so obviously conf''''' is totally rediculious and the program
+                } conf'''''
+  -- Yeah yeah, so obviously conf'''''' is totally rediculious and the program
   -- configuration needs to be in a state monad. That is exactly the plan
   -- (along with some other stuff to give Cabal a better DSL).
 
@@ -213,7 +217,7 @@ configure verbosity hcPath hcPkgPath conf = do
         compilerId             = CompilerId GHC ghcVersion,
         compilerExtensions     = languageExtensions
       }
-  return (comp, conf''''')
+  return (comp, conf'''''')
 
 -- | Given something like /usr/local/bin/ghc-6.6.1(.exe) we try and find a
 -- corresponding ghc-pkg, we try looking for both a versioned and unversioned