The existing code gives a build error against LLVM trunk.

Actually, the latest LLVM trunk causes a lot more Subzero build problems, but if we roll LLVM back to 1d79fff9e65e77f84bf80c2cf4f0155bd167c90d, everything builds except for this one issue.

BUG= none
R=kschimpf@google.com

Review-Url: https://codereview.chromium.org/2598263002 .