[clang] [HIP][SPIRV] Enable the SPIRV backend instead of the translator through an experimental flag. (PR #162282)

[Manuel Carrasco via cfe-commits]

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@@ -1421,6 +1421,16 @@ def fhip_emit_relocatable : Flag<["-"], "fhip-emit-relocatable">,
   HelpText<"Compile HIP source to relocatable">;
 def fno_hip_emit_relocatable : Flag<["-"], "fno-hip-emit-relocatable">,
   HelpText<"Do not override toolchain to compile HIP source to relocatable">;
+def use_experimental_spirv_backend
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mgcarrasco wrote:

Ty. If we don't require a member variable, then `defm` does not seem to be the right option (see how `gpu_bundle_output` and `no_gpu_bundle_output` are defined).

https://github.com/llvm/llvm-project/pull/162282