[clang] [HIP] Pass `-O0` by default for HIP no-RDC compilations (PR #211790)

[Joseph Huber via cfe-commits]

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@@ -9896,6 +9892,12 @@ void LinkerWrapper::ConstructJob(Compilation &C, const JobAction &JA,
         }
       }
 
+      // If no optimization level was requested we default to `-O0` for no-RDC
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jhuber6 wrote:

It's mostly a customer complaint about `clang -O0` and `clang` emitting different DWARF information due to IPO passes changing function signatures in `lto<O2>` even with `optnone`. I have https://github.com/llvm/llvm-project/pull/211804 as the alternate solution, which I prefer heavily to this one.

https://github.com/llvm/llvm-project/pull/211790