[clang] [clang][HIP] Normalize __cdecl on abstract function types to the device default CC on amdgcnspirv (PR #210882)

[Arseniy Obolenskiy via cfe-commits]

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@@ -1787,6 +1787,15 @@ class TargetInfo : public TransferrableTargetInfo,
     }
   }
 
+  /// Determines whether a call using the given calling convention may be
+  /// variadic on this target. Unlike the target-agnostic
+  /// supportsVariadicCall(), this allows a target to reject its own default
+  /// calling convention (e.g. when that default is only nominally CC_C but
+  /// lowers to an ABI that cannot support variadic calls).
+  virtual bool supportsCallingConvVariadic(CallingConv CC) const {
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aobolensk wrote:

`supportsVariadicCall` looks good, renamed

https://github.com/llvm/llvm-project/pull/210882