[clang] [SYCL][Driver] Set -std=c++17 as default for SYCL compilations (PR #194014)

[Srividya Sundaram via cfe-commits]

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@@ -4998,7 +4998,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   }
 
   const llvm::Triple *AuxTriple =
-      (IsCuda || IsHIP) ? TC.getAuxTriple() : nullptr;
+      (IsCuda || IsHIP || IsSYCL) ? TC.getAuxTriple() : nullptr;
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srividya-sundaram wrote:

No, this ensures `-fms-extensions` is passed for both host and device compilation. 
Prior to this patch, `AuxTriple` was set to nullptr for SYCL
By including `IsSYCL` in the `AuxTriple` initialization (L5001), `IsWindowsMSVC` is set based on the host triple for both compilation paths, which then triggers the `-fms-extensions` flag (L7344).


https://github.com/llvm/llvm-project/pull/194014