Use files in path['checkout'] not resource.

scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_win_swarming.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]\\win_swarming",
       "511"
     ],
     "name": "makedirs checkout path",
@@ skipping 248 matching lines @@
     "name": "compile",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output (invalid)@null@@@",
       "@@@STEP_LOG_END@json.output (invalid)@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
-      "RECIPE_MODULE[build::isolate]\\resources\\remove_build_metadata.py",
+      "[BUILDER_CACHE]\\win_swarming\\src\\tools\\determinism\\remove_build_metadata.py",
       "--build-dir",
-      "[BUILDER_CACHE]\\win_swarming\\src\\out\\Debug",
-      "--src-dir",
-      "[BUILDER_CACHE]\\win_swarming\\src"
+      "[BUILDER_CACHE]\\win_swarming\\src\\out\\Debug"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "remove_build_metadata"
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::isolate]\\resources\\isolate.py",
       "[BUILDER_CACHE]\\win_swarming\\src\\tools\\swarming_client",
@@ skipping 2165 matching lines @@
       "@@@STEP_LOG_END@json.output@@@",
       "@@@STEP_LINK@shard #0 isolated out@blah@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]