Update V8 DEPS.

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/fa87ce6..b471e77

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

Change-Id: Ie8d912df3b6c2cdb4688fca4070e58734ed412f1
Reviewed-on: https://chromium-review.googlesource.com/c/1350269Reviewed-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@{#57808}

DEPS

@@ -13,7 +13,7 @@ vars = {
 
 deps = {
   'v8/build':
-    Var('chromium_url') + '/chromium/src/build.git' + '@' + 'fa87ce6fc2aa77772b0f122f602417759e1162f5',
+    Var('chromium_url') + '/chromium/src/build.git' + '@' + 'b471e777a12af28d5f1fa07d5a320a82c67e7ff6',
   'v8/third_party/depot_tools':
     Var('chromium_url') + '/chromium/tools/depot_tools.git' + '@' + '6c18a1afa1a7a30421775c8d6c1cfb7edb3f272a',
   'v8/third_party/icu':