Update V8 DEPS.

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/9baa370..7db6cfc

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

Change-Id: I11f6f1b06a50204af8a01c22324a187536697e6f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1557341Reviewed-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@{#60670}

DEPS

@@ -57,7 +57,7 @@ vars = {
 
 deps = {
   'v8/build':
-    Var('chromium_url') + '/chromium/src/build.git' + '@' + '9baa370a9e10dc9cb3bb101f24b6eb5ba798cf7e',
+    Var('chromium_url') + '/chromium/src/build.git' + '@' + '7db6cfc390a8c0336836472b1c15a062a24ba633',
   'v8/third_party/depot_tools':
     Var('chromium_url') + '/chromium/tools/depot_tools.git' + '@' + '0b62ed79ed5049332f58c06dbdb8e8bc4105010e',
   'v8/third_party/icu':