ci: Enable windows tests for 9.6.3

There were two failing tests:

1. CCompilerOverride, was attempting to use gcc.exe rather than
   clang.exe without also overriding the C options which led to
   incorrect options being passed to gcc.exe. The fix is to override to
   clang.exe on ghc-9.4 or newer.
2. ForeignLibs exposes a bug in GHC
   (https://gitlab.haskell.org/ghc/ghc/-/issues/24185) and hence is
   skipped for GHCs newer than 9.4 where it was first introduced.

Towards fixing haskell#8451, we just need to fix the shared library issue now.

.github/workflows/validate.yml

@@ -166,15 +166,13 @@ jobs:
         # Have to disable *-suite validation:
         # - the Windows@9.6.1 problem is tracked at https://github.com/haskell/cabal/issues/8858
         # - but curently can't run it with GHC 9.6, tracking: https://github.com/haskell/cabal/issues/8883
-        if: (runner.os != 'Windows')  || (matrix.ghc != '9.6.3')
         run: sh validate.sh $FLAGS -s lib-suite
 
       - name: Validate cli-tests
         run: sh validate.sh $FLAGS -s cli-tests
 
       - name: Validate cli-suite
         # Have to disable *-suite validation, see above the comment for lib-suite
-        if: (runner.os != 'Windows')  || (matrix.ghc != '9.6.3')
         run: sh validate.sh $FLAGS -s cli-suite
 
   validate-old-ghcs:

cabal-testsuite/PackageTests/CCompilerOverride/custom-cc-clang.bat

@@ -0,0 +1,11 @@
+@echo OFF
+
+where /q clang.exe
+
+IF %ERRORLEVEL% EQU 0 (
+   call clang.exe -DNOERROR6 %*
+   EXIT /B %ERRORLEVEL%
+)
+
+ECHO "Cannot find C compiler"
+EXIT /B 1

cabal-testsuite/PackageTests/CCompilerOverride/setup.test.hs

@@ -6,16 +6,17 @@ import Test.Cabal.Prelude
 main = setupAndCabalTest $ do
   skipUnlessGhcVersion ">= 8.8"
   isWin <- isWindows
-  ghc94 <- isGhcVersion "== 9.4.*"
+  ghc94 <- isGhcVersion ">= 9.4.1"
   env   <- getTestEnv
   let pwd      = testCurrentDir env
-      customCC = pwd ++ "/custom-cc" ++ if isWin then ".bat" else ""
+      win_suffix = if ghc94 then "-clang.bat" else ".bat"
+      customCC =
+        pwd ++ "/custom-cc" ++ if isWin then win_suffix else ""
 
-  expectBrokenIf (isWin && ghc94) 8451 $ do
-    setup "configure"
-      [ "--ghc-option=-DNOERROR1"
-      , "--ghc-option=-optc=-DNOERROR2"
-      , "--ghc-option=-optP=-DNOERROR3"
-      , "--with-gcc=" ++ customCC
-      ]
-    setup "build" ["-v2"]
+  setup "configure"
+    [ "--ghc-option=-DNOERROR1"
+    , "--ghc-option=-optc=-DNOERROR2"
+    , "--ghc-option=-optP=-DNOERROR3"
+    , "--with-gcc=" ++ customCC
+    ]
+  setup "build" ["-v2"]

cabal-testsuite/PackageTests/ForeignLibs/setup.test.hs

@@ -17,6 +17,7 @@ import Distribution.Simple.Program.Types
 import Distribution.System
 import Distribution.Verbosity
 import Distribution.Version
+import System.Directory
 
 import Test.Cabal.Prelude
 
@@ -27,7 +28,7 @@ main = setupAndCabalTest . recordMode DoNotRecord $ do
   -- Foreign libraries don't work with GHC 7.6 and earlier
   skipUnlessGhcVersion ">= 7.8"
   win <- isWindows
-  ghc94 <- isGhcVersion "== 9.4.*"
+  ghc94 <- isGhcVersion ">= 9.4.1"
   expectBrokenIf (win && ghc94) 8451 $
     withPackageDb $ do
         setup_install []