[LinkerWrapper] Use the correct empty file on Windows (llvm#84322)

Summary:
The clang-offload-bundler uses an empty file to control the bundles made
for embedding. Previously this still used `/dev/null` by mistake even on
Windows.

clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp

@@ -410,7 +410,11 @@ fatbinary(ArrayRef<std::pair<StringRef, StringRef>> InputFiles,
     Targets.push_back(Saver.save("hipv4-amdgcn-amd-amdhsa--" + Arch));
   CmdArgs.push_back(Saver.save(llvm::join(Targets, ",")));
 
+#ifdef _WIN32
+  CmdArgs.push_back("-input=NUL");
+#else
   CmdArgs.push_back("-input=/dev/null");
+#endif
   for (const auto &[File, Arch] : InputFiles)
     CmdArgs.push_back(Saver.save("-input=" + File));