Avoid to use environment.

scripts/slave/recipes/findit/chromium/compile.expected/compile_affected_targets_only.json

 [
   {
     "cmd": [
       "/opt/infra-tools/buildbucket",
       "get",
       "--host",
       "cr-buildbucket.appspot.com",
       "id1"
     ],
     "name": "buildbucket.get",
@@ skipping 689 matching lines @@
       "--gsutil-py-path",
       "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "--ninja-path",
       "RECIPE_PACKAGE_REPO[depot_tools]/ninja",
       "--target",
       "Release",
       "--src-dir",
       "[BUILDER_CACHE]/linux/src",
       "--goma-cache-dir",
       "[GOMA_CACHE]",
+      "--buildbot-buildername",
+      "linux_variable",
+      "--buildbot-mastername",
+      "tryserver.chromium.linux",
+      "--buildbot-slavename",
+      "build1-a1",
       "--goma-deps-cache-dir",
       "[GOMA_DEPS_CACHE]",
       "--compiler",
       "goma",
       "--goma-jsonstatus",
       "/path/to/tmp/json",
       "--goma-service-account-json-file",
       "/creds/service_accounts/service-account-goma-client.json",
       "--goma-dir",
       "[CACHE]/cipd/goma",
@@ skipping 38 matching lines @@
       "@@@STEP_LOG_END@report@@@",
       "@@@SET_BUILD_PROPERTY@report@{\"metadata\": {\"regression_range_size\": 1, \"sub_ranges\": [[null, \"r1\"]], \"use_bisect\": false}, \"result\": {\"r1\": \"passed\"}}@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]