chromium.run_mb: set cwd to checkout

scripts/slave/recipe_modules/chromium/api.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import re
 
 from recipe_engine import recipe_api
 from recipe_engine import util as recipe_util
 
 class TestLauncherFilterFileInputPlaceholder(recipe_util.InputPlaceholder):
@@ skipping 608 matching lines @@
     args += [build_dir]
 
     # This runs with an almost-bare env being passed along, so we get a clean
     # environment without any GYP_DEFINES being present to cause confusion.
     step_kwargs = {
       'name': name or 'generate_build_files',
       'script': self.m.path['checkout'].join('tools', 'mb', 'mb.py'),
       'args': args,
       'env': {
         'GOMA_SERVICE_ACCOUNT_JSON_FILE': self.m.goma.service_account_json_path,
-      }
+      },
+      'cwd': self.m.path['checkout'],
     }
     if self.c.env.FORCE_MAC_TOOLCHAIN:
       step_kwargs['env']['FORCE_MAC_TOOLCHAIN'] = (
         self.c.env.FORCE_MAC_TOOLCHAIN)
 
     if self.c.gyp_env.GYP_MSVS_VERSION:
       # TODO(machenbach): Remove this as soon as it's not read anymore by
       # vs_toolchain.py (currently called by gn).
       step_kwargs['env']['GYP_MSVS_VERSION'] = (
         self.c.gyp_env.GYP_MSVS_VERSION)
@@ skipping 136 matching lines @@
       }))
 
   def get_annotate_by_test_name(self, test_name):
     return 'graphing'
 
   def download_lto_plugin(self):
     return self.m.python(
         name='download LTO plugin',
         script=self.m.path['checkout'].join(
             'build', 'download_gold_plugin.py'))