Recipes: make cwd default to slave_build

scripts/slave/recipes/skia/autoroll.expected/AutoRoll_stopped.json

Index: scripts/slave/recipes/skia/autoroll.expected/AutoRoll_stopped.json
diff --git a/scripts/slave/recipes/skia/autoroll.expected/AutoRoll_stopped.json b/scripts/slave/recipes/skia/autoroll.expected/AutoRoll_stopped.json
index 2e07b7fc0d69d6a3c900071b5b1ce533a19e26c1..94a1a9eefb883eca128865360a4a4b96760e4c4f 100644
--- a/scripts/slave/recipes/skia/autoroll.expected/AutoRoll_stopped.json
+++ b/scripts/slave/recipes/skia/autoroll.expected/AutoRoll_stopped.json
@@ -8,6 +8,7 @@
       "--spec",
       "cache_dir = None\nsolutions = [{'deps_file': 'DEPS', 'managed': True, 'name': 'src', 'url': 'https://chromium.googlesource.com/chromium/src.git'}]"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "gclient setup"
   },
   {
@@ -23,6 +24,7 @@
       "--output-json",
       "/path/to/tmp/json"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "gclient sync",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
@@ -69,6 +71,7 @@
       "http://skia-tree-status.appspot.com/arb_is_stopped",
       "/path/to/tmp/json"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "is_stopped",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
@@ -105,6 +108,7 @@
       "/path/to/tmp/json",
       "[DEPOT_TOOLS]"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "stop_roll",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",