Do not start goma in ChromeOS gclient runhook if gomadir is given.

scripts/slave/recipes/chromium.expected/full_chromium_chromiumos_ChromiumOS_amd64_generic_Compile.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]/ChromiumOS_amd64_generic_Compile",
       "511"
     ],
     "name": "makedirs checkout path",
@@ skipping 171 matching lines @@
   {
     "cmd": [
       "RECIPE_PACKAGE_REPO[depot_tools]/cros",
       "chrome-sdk",
       "--board=amd64-generic",
       "--nocolor",
       "--use-external-config",
       "--clear-sdk-cache",
       "--gomadir",
       "[CACHE]/cipd/goma",
+      "--nostart-goma",
       "--",
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[depot_tools]/gclient.py",
       "runhooks"
     ],
     "cwd": "[BUILDER_CACHE]/ChromiumOS_amd64_generic_Compile/src",
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
       "GYP_CHROMIUM_NO_ACTION": "1",
@@ skipping 52 matching lines @@
   {
     "cmd": [
       "RECIPE_PACKAGE_REPO[depot_tools]/cros",
       "chrome-sdk",
       "--board=amd64-generic",
       "--nocolor",
       "--use-external-config",
       "--clear-sdk-cache",
       "--gomadir",
       "[CACHE]/cipd/goma",
+      "--nostart-goma",
       "--",
       "python",
       "-u",
       "[BUILDER_CACHE]/ChromiumOS_amd64_generic_Compile/src/tools/mb/mb.py",
       "gen",
       "-m",
       "chromium.chromiumos",
       "-b",
       "ChromiumOS amd64-generic Compile",
       "--config-file",
@@ skipping 10 matching lines @@
   },
   {
     "cmd": [
       "RECIPE_PACKAGE_REPO[depot_tools]/cros",
       "chrome-sdk",
       "--board=amd64-generic",
       "--nocolor",
       "--use-external-config",
       "--gomadir",
       "[CACHE]/cipd/goma",
+      "--nostart-goma",
       "--",
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]/scripts/tools/runit.py",
       "--show-path",
       "python",
       "RECIPE_PACKAGE_REPO[build]/scripts/slave/compile.py",
       "--gsutil-py-path",
       "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "--ninja-path",
@@ skipping 67 matching lines @@
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"build_data_dir\": \"[ROOT]/build_data_dir\", \"buildername\": \"ChromiumOS amd64-generic Compile\", \"buildnumber\": 571, \"mastername\": \"chromium.chromiumos\", \"parent_buildername\": null, \"path_config\": \"kitchen\", \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}"
     ],
     "name": "package build"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]