Adds battor_agent to the list of targets built by all trybots

testing/buildbot/chromium.mac.json

 {
+  "Mac Builder": {
+    "additional_compile_targets": [
+      "battor_agent"
+    ]
+  },
   "Mac GN": {
     "additional_compile_targets": [
       "gn_all"
     ],
     "gtest_tests": [
       {
         "test": "base_unittests"
       }
     ]
   },
@@ skipping 1877 matching lines @@
       }
     ],
     "scripts": [
       {
         "name": "nacl_integration",
         "script": "nacl_integration.py"
       }
     ]
   }
 }