hadrian: Package mingw toolchain in expected location

This fixes #24525, a regression due to 41cbaf44.
Specifically, GHC expects to find the mingw32 toolchain in the binary distribution
root. However, after this patch it was packaged in the `lib/` directory.

hadrian/src/Rules/BinaryDist.hs

@@ -135,7 +135,8 @@ bindistRules = do
         let ghcVersionPretty = "ghc-" ++ version ++ "-" ++ targetPlatform
         let prefix = cwd -/- root -/- "reloc-bindist" -/- ghcVersionPretty
         installTo Relocatable prefix
-
+        copyDirectory (root -/- "mingw") prefix
+        liftIO $ IO.removeDirectoryRecursive (prefix -/- "lib" -/- "mingw")
 
     phony "install" $ do
         need ["binary-dist-dir"]
@@ -145,8 +146,6 @@ bindistRules = do
         installTo NotRelocatable installPrefix
 
     phony "binary-dist-dir" $ do
-
-
         version        <- setting ProjectVersion
         targetPlatform <- setting TargetPlatformFull
         distDir        <- Context.distDir Stage1
@@ -309,7 +308,7 @@ bindistRules = do
 
     let buildBinDist compressor = do
           win_target <- isWinTarget
-          when win_target (error "normal binary-dist does not work for windows target, use `reloc-binary-dist-*` target instead.")
+          when win_target (error "normal binary-dist does not work for Windows targets, use `reloc-binary-dist-*` target instead.")
           buildBinDistX "binary-dist-dir" "bindist" compressor
         buildBinDistReloc = buildBinDistX "reloc-binary-dist-dir" "reloc-bindist"