Adds ability for builders to only compile targets affected by change

scripts/slave/recipes/chromium_trybot.expected/compile_because_of_analyze.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "tryserver.chromium.linux",
       "--builder",
       "linux_chromium_rel",
@@ skipping 105 matching lines @@
       "--analyzer",
       "{\"files\": [\"foo.cc\"], \"targets\": []}",
       "/path/to/tmp/json"
     ],
     "env": {
       "GYP_DEFINES": "component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' target_arch=x64 use_goma=1"
     },
     "name": "analyze",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
+      "@@@STEP_LOG_LINE@json.output@  \"build_targets\": [], @@@",
       "@@@STEP_LOG_LINE@json.output@  \"status\": \"Found dependency\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"targets\": []@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
@@ skipping 177 matching lines @@
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/mojo/tools/run_mojo_python_tests.py",
       "--write-full-results-to",
       "/path/to/tmp/json"
     ],
     "name": "mojo_python_tests (with patch)"
   }
 ]