Adds battor_agent to the list of targets built by all trybots

testing/buildbot/chromium.linux.json

 {
   "Android GN": {
     "additional_compile_targets": [
       "all"
     ],
     "gtest_tests": [
       {
         "test": "base_unittests"
       },
       {
@@ skipping 283 matching lines @@
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "url_unittests"
       }
     ]
   },
   "Linux Builder": {
     "additional_compile_targets": [
+      "battor_agent",
       "blimp",
       "mandoline:all",
       "mash:all",
       "remoting_all"
     ]
   },
   "Linux Builder (dbg)": {
     "additional_compile_targets": [
       "gn_all"
     ]
@@ skipping 1105 matching lines @@
       }
     ],
     "scripts": [
       {
         "name": "nacl_integration",
         "script": "nacl_integration.py"
       }
     ]
   }
 }