try fixing windows test suite

Test suite is failing in windows in conflict resolution tests, where the
automatic conflict resolution adds in a .variant file. On windows, those
files are somehow missing. I don't understand why, and the test failures
only happen on appveyor and not in a local windows VM.

So, since replaceFile was recently changed to remove a windows specific
ifdef, put it back, to see if that is somehow causing these failures.

Annex/ReplaceFile.hs

@@ -5,6 +5,8 @@
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
+{-# LANGUAGE CPP #-}
+
 module Annex.ReplaceFile (
 	replaceGitAnnexDirFile,
 	replaceGitDirFile,
@@ -57,7 +59,11 @@ replaceFile createdirectory file action = replaceFile' createdirectory file (con
 
 replaceFile' :: (RawFilePath -> Annex ()) -> RawFilePath -> (a -> Bool) -> (RawFilePath -> Annex a) -> Annex a
 replaceFile' createdirectory file checkres action = withOtherTmp $ \othertmpdir -> do
+#ifndef mingw32_HOST_OS
 	let basetmp = relatedTemplate' (P.takeFileName file)
+#else
+	let basetmp = toRawFilePath "t"
+#endif
 	withTmpDirIn (fromRawFilePath othertmpdir) (toOsPath basetmp) $ \tmpdir -> do
 		let tmpfile = toRawFilePath tmpdir P.</> basetmp
 		r <- action tmpfile