Roll recipe dependencies (nontrivial).

scripts/slave/recipes/cros/cbuildbot_tryjob.expected/external.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "chromiumos.tryserver",
       "--builder",
       "full",
       "--slave",
       "test",
       "--spec",
       "cache_dir = '[GIT_CACHE]'\nsolutions = [{'deps_file': 'DEPS', 'managed': True, 'name': 'chromite', 'url': 'https://chromium.googlesource.com/chromiumos/chromite.git'}]",
       "--root",
       "chromite",
       "--revision_mapping_file",
       "{}",
       "--git-cache-dir",
       "[GIT_CACHE]",
       "--output_json",
       "/path/to/tmp/json",
       "--revision",
       "chromite@master:",
       "--force",
       "--output_manifest"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "env": {
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "bot_update",
     "~followup_annotations": [
       "@@@STEP_TEXT@Some step text@@@",
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"did_run\": true, @@@",
       "@@@STEP_LOG_LINE@json.output@  \"fixed_revisions\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"chromite\": \"master:\"@@@",
@@ skipping 26 matching lines @@
     "name": "sync chromite branch [master]"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "[SLAVE_BUILD]/chromite/cbuildbot/config_dump.json",
       "/path/to/tmp/json"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "read chromite config",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@config@{@@@",
       "@@@STEP_LOG_LINE@config@  \"x86-generic-full\": {@@@",
       "@@@STEP_LOG_LINE@config@    \"_template\": \"full\", @@@",
       "@@@STEP_LOG_LINE@config@    \"type\": \"full\"@@@",
       "@@@STEP_LOG_LINE@config@  }@@@",
       "@@@STEP_LOG_LINE@config@}@@@",
       "@@@STEP_LOG_END@config@@@"
     ]
@@ skipping 12 matching lines @@
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "cbuildbot [x86-generic-full]"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]