Run the Mac impeller-cmake-example orchestrator on arm64

Author: zanderso

.ci.yaml

@@ -445,11 +445,12 @@ targets:
         ]
 
   - name: Mac impeller-cmake-example
-    bringup: true
+    #bringup: true
     recipe: engine_v2/engine_v2
     timeout: 60
     properties:
       release_build: "true"
+      cpu: arm64
       config_name: mac_impeller_cmake_example
       $flutter/osx_sdk : >-
         { "sdk_version": "14a5294e" }