Revert "Remove the Windows GCC driver."

This reverts commit d6cecde585b0980ed8e0050c5a1d315789fb6356.

The patch broke Simon PJ's Windows build, becuase he didn't
have (and should not need) a separate msys2 gcc.

Following an exchange on the ghc-devs list, Tamar wrote

  Oops, sorry, didn’t notice it because both mine and harbormaster’s
  msys2 have separate GCCs installed as well.

  I don’t see an easy fix that would also work for end user Configure
  based cabal installs. So I think I’ll have to go back to the drawing
  board for this one.

  You can just leave it reverted.

1 files changed, 13 insertions, 25 deletions

diff --git a/compiler/main/SysTools.hs b/compiler/main/SysTools.hs
index f2878b0e7b..0a19feb2ce 100644
--- a/compiler/main/SysTools.hs
+++ b/compiler/main/SysTools.hs
@@ -202,10 +202,17 @@ initSysTools mbMinusB
                             Nothing ->
                                 pgmError ("Can't parse " ++
                                           show platformConstantsFile)
-       let getSettingRaw key = case lookup key mySettings of
-                                 Just xs -> return xs
-                                 Nothing -> pgmError ("No entry for " ++ show key ++ " in " ++ show settingsFile)
-           getSetting key = resolveTopDir top_dir <$> getSettingRaw key
+       let getSetting key = case lookup key mySettings of
+                            Just xs ->
+                                return $ case stripPrefix "$topdir" xs of
+                                         Just [] ->
+                                             top_dir
+                                         Just xs'@(c:_)
+                                          | isPathSeparator c ->
+                                             top_dir ++ xs'
+                                         _ ->
+                                             xs
+                            Nothing -> pgmError ("No entry for " ++ show key ++ " in " ++ show settingsFile)
            getBooleanSetting key = case lookup key mySettings of
                                    Just "YES" -> return True
                                    Just "NO" -> return False
@@ -232,11 +239,7 @@ initSysTools mbMinusB
        -- with the settings file, but it would be a little fiddly
        -- to make that possible, so for now you can't.
        gcc_prog <- getSetting "C compiler command"
-       -- TopDir can expand to something that contains spaces
-       -- for the argument string we apply words to the string in order to
-       -- break it up. So defer the expansion of $TopDir till after the words
-       -- call here.
-       gcc_args_str <- getSettingRaw "C compiler flags"
+       gcc_args_str <- getSetting "C compiler flags"
        gccSupportsNoPie <- getBooleanSetting "C compiler supports -no-pie"
        cpp_prog <- getSetting "Haskell CPP command"
        cpp_args_str <- getSetting "Haskell CPP flags"
@@ -249,7 +252,7 @@ initSysTools mbMinusB
                = ["-DTABLES_NEXT_TO_CODE"]
             | otherwise = []
            cpp_args= map Option (words cpp_args_str)
-           gcc_args = map (Option . resolveTopDir top_dir) (words gcc_args_str
+           gcc_args = map Option (words gcc_args_str
                                ++ unreg_gcc_args
                                ++ tntc_gcc_args)
        ldSupportsCompactUnwind <- getBooleanSetting "ld supports compact unwind"
@@ -360,21 +363,6 @@ initSysTools mbMinusB
                     sPlatformConstants = platformConstants
              }
 
--- | This function will replace any usage of $TopDir in the given string
---   regardless of it's location within the string.
-resolveTopDir :: String -- ^ The value of $TopDir
-              -> String -- ^ The string to perform substitutions in
-              -> String -- ^ The resulting string with all subs done.
-resolveTopDir top_dir str
-  = case break (=='$') str of
-      (_, []) -> str
-      (x, xs) -> let rst = case stripPrefix "$topdir" xs of
-                             Just [] -> top_dir
-                             Just xs'@(c:_) | isPathSeparator c
-                                     -> top_dir ++ xs'
-                             _       -> xs
-                 in x ++ resolveTopDir top_dir rst
-
 -- returns a Unix-format path (relying on getBaseDir to do so too)
 findTopDir :: Maybe String -- Maybe TopDir path (without the '-B' prefix).
            -> IO String    -- TopDir (in Unix format '/' separated)