Recipes: make cwd default to slave_build

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

Index: scripts/slave/recipe_modules/android/example.expected/basic.json
diff --git a/scripts/slave/recipe_modules/android/example.expected/basic.json b/scripts/slave/recipe_modules/android/example.expected/basic.json
index 184418841f0021ac1c8aa97185cbc55cff606aca..6af9c1841c98497de03ac91864ff7621e6858147 100644
--- a/scripts/slave/recipe_modules/android/example.expected/basic.json
+++ b/scripts/slave/recipe_modules/android/example.expected/basic.json
@@ -21,6 +21,7 @@
       "--revision",
       "src@123456"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "bot_update",
     "~followup_annotations": [
       "@@@STEP_TEXT@Some step text@@@",
@@ -42,6 +43,7 @@
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "env": {
       "GYP_CHROMIUM_NO_ACTION": "1"
     },
@@ -55,6 +57,7 @@
       "[SLAVE_BUILD]/android-src",
       "511"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "makedirs android source root",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",
@@ -100,6 +103,7 @@
       "RECIPE_MODULE[android]/resources/update_default_props.py",
       "ro.adb.secure=0"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "update /root/default.prop"
   },
   {
@@ -112,6 +116,7 @@
       "--output-json",
       "/path/to/tmp/json"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "calculate blacklist",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
@@ -136,6 +141,7 @@
       "[SLAVE_BUILD]/src/",
       "[SLAVE_BUILD]/android-src/external/chromium_org"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "rsync chromium_org"
   },
   {