BUILD is already defined in test/cctest/wasm/wasm-run-utils.h.

Bug: chromium:746958
Change-Id: Icf577ce91424d9851d2db39658fd52c68c864995
Reviewed-on: https://chromium-review.googlesource.com/676843Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Mostyn Bramley-Moore <mostynb@opera.com>
Cr-Commit-Position: refs/heads/master@{#48122}