Avoid to use environment.

scripts/slave/recipes/libyuv/libyuv.expected/tryserver_libyuv_win_clang.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]\\resources\\bot_update.py",
       "--master",
       "tryserver.libyuv",
       "--builder",
       "win_clang",
@@ skipping 143 matching lines @@
       "--gsutil-py-path",
       "RECIPE_PACKAGE_REPO[depot_tools]\\gsutil.py",
       "--ninja-path",
       "RECIPE_PACKAGE_REPO[depot_tools]\\ninja.exe",
       "--target",
       "Debug",
       "--src-dir",
       "[SLAVE_BUILD]\\src",
       "--goma-cache-dir",
       "[GOMA_CACHE]",
+      "--buildbot-buildername",
+      "win_clang",
+      "--buildbot-mastername",
+      "tryserver.libyuv",
+      "--buildbot-slavename",
+      "slavename",
       "--compiler",
       "goma-clang",
       "--goma-jsonstatus",
       "/path/to/tmp/json",
       "--goma-service-account-json-file",
       "C:\\creds\\service_accounts\\service-account-goma-client.json",
       "--goma-dir",
       "[CACHE]\\cipd\\goma",
       "--goma-fail-fast",
       "--goma-disable-local-fallback",
@@ skipping 26 matching lines @@
       "libyuv_unittest.exe"
     ],
     "name": "libyuv_unittest"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]