[clang] [clang-repl] : Fix clang-repl crash with --cuda flag (PR #136404)

[Vassil Vassilev via cfe-commits]

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@@ -172,6 +154,19 @@ llvm::Error IncrementalCUDADeviceParser::GenerateFatbinary() {
 
   FatbinContent.append(PTXCode.begin(), PTXCode.end());
 
+  auto &PTU = PTUs.back();
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vgvassilev wrote:

```suggestion
  const PartialTranslationUnit &PTU = PTUs.back();
```

https://github.com/llvm/llvm-project/pull/136404