Update V8 DEPS.

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/9be9e38..c81ea93

TBR=v8-waterfall-sheriff@grotations.appspotmail.com

Change-Id: I636ba44c19f6b96fb1039fa3d3cbc7c92bbaa940
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2899839Reviewed-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@{#74581}

DEPS

@@ -85,7 +85,7 @@ vars = {
 
 deps = {
   'build':
-    Var('chromium_url') + '/chromium/src/build.git' + '@' + '9be9e3818ad37867e50ebeec6884bb73a48eff8f',
+    Var('chromium_url') + '/chromium/src/build.git' + '@' + 'c81ea932910009ab8b785ff4a2728a2b3952a5f3',
   'third_party/depot_tools':
     Var('chromium_url') + '/chromium/tools/depot_tools.git' + '@' + 'cd152033d0a33281e28848a551c7a39e93e91e49',
   'third_party/icu':