Update V8 DEPS.

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/e6adad9..789c8f5

TBR=machenbach@chromium.org,tmrts@chromium.org

Change-Id: Ibb2f7b826ec35925c3ddaef2b8549e7cd5a1ce6e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1908650Reviewed-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@{#64870}

DEPS

@@ -79,7 +79,7 @@ vars = {
 
 deps = {
   'v8/build':
-    Var('chromium_url') + '/chromium/src/build.git' + '@' + 'e6adad90f04b80988fbf4fd4de34b5d87cd8c821',
+    Var('chromium_url') + '/chromium/src/build.git' + '@' + '789c8f54b0dcfcf0eb1fc47de5d1dae2644925e7',
   'v8/third_party/depot_tools':
     Var('chromium_url') + '/chromium/tools/depot_tools.git' + '@' + 'ea1884b651e69975e897b15cf2063f36317538a4',
   'v8/third_party/icu':