windows.crossThreadsStdenv: llvmPackages_8 -> llvmPackages

removing references to llvmPackages_8 in preparation to drop it from the
tree

pkgs/os-specific/windows/default.nix

@@ -17,9 +17,10 @@ lib.makeScope newScope (self: with self; {
     stdenv = crossLibcStdenv;
   };
 
+  # FIXME untested with llvmPackages_16 was using llvmPackages_8
   crossThreadsStdenv = overrideCC crossLibcStdenv
     (if stdenv.hostPlatform.useLLVM or false
-     then buildPackages.llvmPackages_8.clangNoLibcxx
+     then buildPackages.llvmPackages.clangNoLibcxx
      else buildPackages.gccWithoutTargetLibc.override (old: {
        bintools = old.bintools.override {
          libc = libcCross;