Update V8 DEPS.

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/39738e7..89fa02a

TBR=machenbach@chromium.org,hablich@chromium.org,sergiyb@chromium.org

Change-Id: I1e1b8d8fa430e7ecc4ce6fe57de64ff7442245c2
Reviewed-on: https://chromium-review.googlesource.com/920706Reviewed-by: v8 autoroll <v8-autoroll@chromium.org>
Commit-Queue: v8 autoroll <v8-autoroll@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51303}

DEPS

@@ -13,7 +13,7 @@ vars = {
 
 deps = {
   'v8/build':
-    Var('chromium_url') + '/chromium/src/build.git' + '@' + '39738e75b27f39d4c0030a0b11d5d2ddd34715f7',
+    Var('chromium_url') + '/chromium/src/build.git' + '@' + '89fa02a2cd3ef0879b6981b74ea38b4c172a58db',
   'v8/tools/gyp':
     Var('chromium_url') + '/external/gyp.git' + '@' + 'd61a9397e668fa9843c4aa7da9e79460fe590bfb',
   'v8/third_party/icu':