Increase the execution timeout for mac-arm64-rel-tests.

mac-arm64-rel-tests will be modified to serialize tests, which has the
potential to dramtically increase the execution time. The timeout is
being doubled to hopefully provide sufficient headroom for the time to
serially execute the tests.

Bug: 1139038
Change-Id: I904a7b9835b61cec053de28663df5ce5fe6a6315
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2481068
Auto-Submit: Garrett Beaty <gbeaty@chromium.org>
Reviewed-by: Erik Staab <estaab@chromium.org>
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818017}

infra/config/generated/cr-buildbucket.cfg

@@ -14440,7 +14440,7 @@ buckets {
         cmd: "recipes"
       }
       properties: "{\"$build/goma\":{\"use_luci_auth\":true},\"$kitchen\":{\"devshell\":true,\"git_auth\":true},\"$recipe_engine/isolated\":{\"server\":\"https://isolateserver.appspot.com\"},\"builder_group\":\"chromium.fyi\",\"recipe\":\"chromium\"}"
-      execution_timeout_secs: 10800
+      execution_timeout_secs: 21600
       build_numbers: YES
       service_account: "chromium-ci-builder@chops-service-accounts.iam.gserviceaccount.com"
       experiments {

infra/config/subprojects/chromium/ci.star

@@ -4328,6 +4328,9 @@ ci.thin_tester(
         category = "mac",
         short_name = "a64",
     ),
+    # TODO(gbeaty) Once we have sufficient test capacity to not need to
+    # serialize tests, use the default execution_timout
+    execution_timeout = 6 * time.hour,
     tree_closing = False,
     triggered_by = [builder_name("mac-arm64-rel")],
 )