Tree is blocked on `Mac_x64 tool_tests_commands` and `Mac_arm64 tool_tests_commands` failures

These are failing in both presubmit and postsubmit.

Example: https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8709004025542628929/+/u/run_test.dart_for_tool_tests_shard_and_subshard_commands/stdout

The failures started with https://github.com/flutter/flutter/pull/172316 which is a doc-only change, so that's probably not the cause.

cc @dkwingsmt @bkonyi 