Adds battor_agent to the list of targets built by all trybots

testing/buildbot/chromium.win.json

 {
   "Vista Tests (1)": {
     "gtest_tests": [
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "accessibility_unittests"
       },
       {
@@ skipping 707 matching lines @@
         }
       }
     ],
     "scripts": [
       {
         "name": "nacl_integration",
         "script": "nacl_integration.py"
       }
     ]
   },
+  "Win Builder": {
+    "additional_compile_targets": [
+      "battor_agent"
+    ]
+  },
   "Win x64 GN": {
     "additional_compile_targets": [
       "gn_all"
     ]
   },
   "Win x64 GN (dbg)": {
     "additional_compile_targets": [
       "accessibility_unittests",
       "app_list_unittests",
       "app_shell_unittests",
@@ skipping 1288 matching lines @@
       }
     ],
     "scripts": [
       {
         "name": "nacl_integration",
         "script": "nacl_integration.py"
       }
     ]
   }
 }