Update V8 DEPS.

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/86e6b5e..63f397a

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

Change-Id: Iff11ed400b0e9440fa03f8b783e4ae4308c0166c
Reviewed-on: https://chromium-review.googlesource.com/c/1267656
Commit-Queue: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#56429}

DEPS

@@ -13,7 +13,7 @@ vars = {
 
 deps = {
   'v8/build':
-    Var('chromium_url') + '/chromium/src/build.git' + '@' + '86e6b5ea07f17ec651f63e861778fb55f2ce0579',
+    Var('chromium_url') + '/chromium/src/build.git' + '@' + '63f397a2dfe553dfa9144507429d0bf05f948246',
   'v8/third_party/depot_tools':
     Var('chromium_url') + '/chromium/tools/depot_tools.git' + '@' + '71e3be7a50c21faeee91ed99a8d5addfb7594e7c',
   'v8/third_party/icu':