Recipes: make cwd default to slave_build

scripts/slave/recipe_modules/gclient/example.expected/basic.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "config",
       "--spec",
       "cache_dir = '[ROOT]/git_cache'\nsolutions = [{'deps_file': '.DEPS.git', 'managed': True, 'name': 'src', 'url': 'https://chromium.googlesource.com/chromium/src.git'}]"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "gclient setup"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "sync",
       "--verbose",
       "--with_branch_heads",
       "--nohooks",
       "-j8",
       "--reset",
       "--force",
       "--upstream",
       "--no-nag-max",
       "--delete_unversioned_trees",
       "--output-json",
       "/path/to/tmp/json"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "gclient sync",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"solutions\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"src/\": {@@@",
       "@@@STEP_LOG_LINE@json.output@      \"revision\": \"f27fede2220bcd326aee3e86ddfd4ebd0fe58cb9\"@@@",
       "@@@STEP_LOG_LINE@json.output@    }@@@",
       "@@@STEP_LOG_LINE@json.output@  }@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "recurse",
       "git",
       "config",
       "user.name",
       "local_bot"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "gclient recurse (git config user.name)"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "recurse",
       "git",
       "config",
       "user.email",
       "local_bot@example.com"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "gclient recurse (git config user.email)"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "config",
       "--spec",
       "cache_dir = None\nsolutions = [{'deps_file': 'DEPS', 'managed': True, 'name': 'WebKit', 'safesync_url': 'https://blink-status.appspot.com/lkgr', 'url': 'svn://svn.chromium.org/blink/trunk'}]"
@@ skipping 31 matching lines @@
       "@@@SET_BUILD_PROPERTY@got_blatley_revision@248087@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport os, sys\n\nbuild_path = sys.argv[1]\nif os.path.exists(build_path):\n  for (path, dir, files) in os.walk(build_path):\n    for cur_file in files:\n      if cur_file.endswith('index.lock'):\n        path_to_file = os.path.join(path, cur_file)\n        print 'deleting %s' % path_to_file\n        os.remove(path_to_file)\n",
       "[SLAVE_BUILD]"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "cleanup index.lock",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",
       "@@@STEP_LOG_LINE@python.inline@import os, sys@@@",
       "@@@STEP_LOG_LINE@python.inline@@@@",
       "@@@STEP_LOG_LINE@python.inline@build_path = sys.argv[1]@@@",
       "@@@STEP_LOG_LINE@python.inline@if os.path.exists(build_path):@@@",
       "@@@STEP_LOG_LINE@python.inline@  for (path, dir, files) in os.walk(build_path):@@@",
       "@@@STEP_LOG_LINE@python.inline@    for cur_file in files:@@@",
       "@@@STEP_LOG_LINE@python.inline@      if cur_file.endswith('index.lock'):@@@",
       "@@@STEP_LOG_LINE@python.inline@        path_to_file = os.path.join(path, cur_file)@@@",
       "@@@STEP_LOG_LINE@python.inline@        print 'deleting %s' % path_to_file@@@",
       "@@@STEP_LOG_LINE@python.inline@        os.remove(path_to_file)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   }
 ]