[clang] [Clang][X86] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow VPERMILPD/S variable mask intrinsics to be used in constexpr (PR #168861)

[Simon Pilgrim via cfe-commits]

https://github.com/RKSimon requested changes to this pull request.

Thanks!

https://github.com/llvm/llvm-project/pull/168861