Recipes: make cwd default to slave_build

scripts/slave/recipes/v8.expected/full_client_v8_V8_Mac64.json

Index: scripts/slave/recipes/v8.expected/full_client_v8_V8_Mac64.json
diff --git a/scripts/slave/recipes/v8.expected/full_client_v8_V8_Mac64.json b/scripts/slave/recipes/v8.expected/full_client_v8_V8_Mac64.json
index 28460407ffebc0a825237b239835a6c4d6a5c59c..b5b6a312c1d9199e3801acb5eb9b184b08dc012d 100644
--- a/scripts/slave/recipes/v8.expected/full_client_v8_V8_Mac64.json
+++ b/scripts/slave/recipes/v8.expected/full_client_v8_V8_Mac64.json
@@ -23,6 +23,7 @@
       "--no_shallow",
       "--output_manifest"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "bot_update",
     "~followup_annotations": [
       "@@@STEP_TEXT@Some step text@@@",
@@ -55,6 +56,7 @@
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "env": {
       "GYP_DEFINES": "clang=1 gomadir='[BUILD]/goma' target_arch=x64 use_goma=1 v8_target_arch=x64",
       "GYP_GENERATORS": "ninja"
@@ -67,6 +69,7 @@
       "-u",
       "[BUILD]/scripts/slave/cleanup_temp.py"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "cleanup_temp"
   },
   {
@@ -86,6 +89,7 @@
       "[BUILD]/goma",
       "--"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "compile"
   },
   {