Fix build config of Headless bot

testing/buildbot/chromium.fyi.json

 {
   "Android Asan Builder Tests (dbg)": {
     "gtest_tests": [
       {
         "args": [
           "--tool=asan"
         ],
         "test": "android_webview_unittests"
       },
       {
@@ skipping 6842 matching lines @@
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "wtf_unittests"
       }
     ]
   },
   "Headless Linux (dbg)": {
     "additional_compile_targets": [
-      "headless_libs",
+      "headless_lib",
       "headless_tests"
     ],
     "gtest_tests": [
       {
         "test": "headless_browsertests"
       },
       {
         "test": "headless_unittests"
       }
     ]
@@ skipping 1509 matching lines @@
       },
       {
         "args": [
           "--isolate-extensions"
         ],
         "test": "unit_tests"
       }
     ]
   }
 }