analyze: set cwd to checkout for TARGET_CROS_BOARD builds

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport sys, os\npath = sys.argv[1]\nmode = int(sys.argv[2])\nif not os.path.isdir(path):\n  if os.path.exists(path):\n    print \"%s exists but is not a dir\" % path\n    sys.exit(1)\n  os.makedirs(path, mode)\n",
       "[BUILDER_CACHE]/chromeos_amd64_generic_chromium_compile_only_ng",
       "511"
     ],
     "name": "makedirs checkout path",
@@ skipping 295 matching lines @@
       "analyze",
       "-m",
       "tryserver.chromium.linux",
       "-b",
       "chromeos_amd64-generic_chromium_compile_only_ng",
       "-v",
       "//out/Release",
       "{\"additional_compile_targets\": [\"chromiumos_preflight\"], \"files\": [\"foo.cc\"], \"test_targets\": []}",
       "/path/to/tmp/json"
     ],
+    "cwd": "[BUILDER_CACHE]/chromeos_amd64_generic_chromium_compile_only_ng/src",
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "analyze",
     "~followup_annotations": [
       "@@@STEP_TEXT@No compile necessary@@@",
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"compile_targets\": [], @@@",
       "@@@STEP_LOG_LINE@json.output@  \"status\": \"No dependency\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"test_targets\": []@@@",
@@ skipping 18 matching lines @@
       "import sys; sys.exit(0)"
     ],
     "name": "mark: before_tests"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]