Fix test/CodeGen/builtins.c for platforms that don't lower sjlj

Opt in Win64 to supporting sjlj lowering. We have the backend lowering,
so I think this was just an oversight because WinX86_64TargetCodeGenInfo
doesn't inherit from X86_64TargetCodeGenInfo.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@231280 91177308-0d34-0410-b5e6-96231b3b80d8