Update V8 DEPS.

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/857a0f2..70f5848

TBR=v8-waterfall-sheriff@grotations.appspotmail.com,mtv-sf-v8-sheriff@grotations.appspotmail.com

Change-Id: Ib38adcb3001d4176cb0b3cd8fb4e0cc54511c910
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3020064Reviewed-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@{#75667}

DEPS

@@ -92,7 +92,7 @@ deps = {
   'base/trace_event/common':
     Var('chromium_url') + '/chromium/src/base/trace_event/common.git' + '@' + 'd5bb24e5d9802c8c917fcaa4375d5239a586c168',
   'build':
-    Var('chromium_url') + '/chromium/src/build.git' + '@' + '857a0f2a938989c6c26e34431217c7c007c7200f',
+    Var('chromium_url') + '/chromium/src/build.git' + '@' + '70f58488ed32737e217005596833f5c0cc919f43',
   'buildtools':
     Var('chromium_url') + '/chromium/src/buildtools.git' + '@' + '2500c1d8f3a20a66a7cbafe3f69079a2edb742dd',
   'buildtools/clang_format/script':