Recipes: make cwd default to slave_build

scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_ios_arm64.json

Index: scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_ios_arm64.json
diff --git a/scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_ios_arm64.json b/scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_ios_arm64.json
index 0754016911c70d2b06269ca36520621072ca5915..ff2d14da0a9daea5dbad03fdf6dfe5b2661ba3fe 100644
--- a/scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_ios_arm64.json
+++ b/scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_ios_arm64.json
@@ -27,6 +27,7 @@
       "--revision",
       "src@12345"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "bot_update",
     "~followup_annotations": [
       "@@@STEP_TEXT@Some step text@@@",
@@ -53,6 +54,7 @@
       "RECIPE_MODULE[webrtc]/resources/cleanup_files.py",
       "[SLAVE_BUILD]/src/out"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "clean test output files"
   },
   {
@@ -61,6 +63,7 @@
       "-u",
       "[BUILD]/scripts/slave/cleanup_temp.py"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "cleanup_temp"
   },
   {
@@ -70,6 +73,7 @@
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "env": {
       "GYP_CROSSCOMPILE": "1",
       "GYP_DEFINES": "OS=ios build_with_libjingle=1 chromium_ios_signing=0 clang=1 component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' key_id='' mac_sdk=10.9 target_arch=arm64 use_goma=1",
@@ -95,6 +99,7 @@
       "--",
       "All"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "compile"
   }
 ]