Update V8 DEPS.

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/4e13e3f..ff2ef81

TBR=machenbach@chromium.org,tmrts@chromium.org,v8-waterfall-sheriff@grotations.appspotmail.com

Change-Id: I4c4f0a80ba0b4dc1e705f5973664a14cc50d6a6c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2609206Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Commit-Queue: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#71900}

DEPS

@@ -88,7 +88,7 @@ vars = {
 
 deps = {
   'build':
-    Var('chromium_url') + '/chromium/src/build.git' + '@' + '4e13e3f7dd3689818d4662e9c853fa75df77f92a',
+    Var('chromium_url') + '/chromium/src/build.git' + '@' + 'ff2ef814963d418b096a23afe8d97df1eda6406f',
   'third_party/depot_tools':
     Var('chromium_url') + '/chromium/tools/depot_tools.git' + '@' + '364205c70ed16c00802b1c264e88d8e03a0b37ae',
   'third_party/icu':