Update V8 DEPS.

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/ff2ef81..46adc39

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

Change-Id: Ic5169bac840db4a0ab25c0b5c8e4ae6166020244
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2609716Reviewed-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@{#71901}

DEPS

@@ -88,7 +88,7 @@ vars = {
 
 deps = {
   'build':
-    Var('chromium_url') + '/chromium/src/build.git' + '@' + 'ff2ef814963d418b096a23afe8d97df1eda6406f',
+    Var('chromium_url') + '/chromium/src/build.git' + '@' + '46adc39ea771b7613e422b6c9ade554e75972b65',
   'third_party/depot_tools':
     Var('chromium_url') + '/chromium/tools/depot_tools.git' + '@' + '364205c70ed16c00802b1c264e88d8e03a0b37ae',
   'third_party/icu':