Update V8 DEPS.

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/ce4fbca..b71c9cc

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

Change-Id: I2c256e47641ea1e5cd1b4496329ecb4f5842076e
Reviewed-on: https://chromium-review.googlesource.com/c/1390200Reviewed-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@{#58457}

DEPS

@@ -16,7 +16,7 @@ vars = {
 
 deps = {
   'v8/build':
-    Var('chromium_url') + '/chromium/src/build.git' + '@' + 'ce4fbcae5d3da9ef1850cd1a70d77daf7fa0ab7b',
+    Var('chromium_url') + '/chromium/src/build.git' + '@' + 'b71c9cc7e8b9cd28c60e4621fdad87c48820a418',
   'v8/third_party/depot_tools':
     Var('chromium_url') + '/chromium/tools/depot_tools.git' + '@' + 'db0055dc786a71fe81e720bad2b1acb0e133a291',
   'v8/third_party/icu':