[clang] [LinkerWrapper] Try to fix testing on Windows (PR #130285)

[Matt Arsenault via cfe-commits]

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@@ -599,9 +599,10 @@ Expected<StringRef> writeOffloadFile(const OffloadFile &File) {
 
   StringRef Prefix =
       sys::path::stem(Binary.getMemoryBufferRef().getBufferIdentifier());
-
-  auto TempFileOrErr = createOutputFile(
-      Prefix + "-" + Binary.getTriple() + "-" + Binary.getArch(), "o");
+  std::string Filename =
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arsenm wrote:

Can you use SmallString? Also is there one of those Path utility functions for this? 

https://github.com/llvm/llvm-project/pull/130285