Recipes: make cwd default to slave_build

scripts/slave/recipes/chromium_gn.expected/full_chromium_linux_Linux_GN__dbg_.json

Index: scripts/slave/recipes/chromium_gn.expected/full_chromium_linux_Linux_GN__dbg_.json
diff --git a/scripts/slave/recipes/chromium_gn.expected/full_chromium_linux_Linux_GN__dbg_.json b/scripts/slave/recipes/chromium_gn.expected/full_chromium_linux_Linux_GN__dbg_.json
index 2e11eef9ed37442971634c18283d3b72f86eaa57..d57556923ce118df49188b6098449f2eaf845b1a 100644
--- a/scripts/slave/recipes/chromium_gn.expected/full_chromium_linux_Linux_GN__dbg_.json
+++ b/scripts/slave/recipes/chromium_gn.expected/full_chromium_linux_Linux_GN__dbg_.json
@@ -22,6 +22,7 @@
       "src@HEAD",
       "--force"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "bot_update",
     "~followup_annotations": [
       "@@@STEP_TEXT@Some step text@@@",
@@ -68,6 +69,7 @@
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "env": {
       "GYP_CHROMIUM_NO_ACTION": "1"
     },
@@ -90,6 +92,7 @@
       "[BUILD]/goma",
       "//out/Debug"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "Generate build files"
   },
   {
@@ -100,6 +103,7 @@
       "[SLAVE_BUILD]/src/testing/buildbot/chromium.linux.json",
       "/path/to/tmp/json"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "read test spec",
     "~followup_annotations": [
       "@@@STEP_TEXT@path: [SLAVE_BUILD]/src/testing/buildbot/chromium.linux.json@@@",
@@ -132,6 +136,7 @@
       "base_unittests",
       "all"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "compile"
   },
   {
@@ -143,6 +148,7 @@
       "check",
       "//out/Debug"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "gn check"
   },
   {
@@ -152,6 +158,7 @@
       "[SLAVE_BUILD]/src/tools/gn/bin/gyp_flag_compare.py",
       "chrome"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "gyp_flag_compare"
   }
 ]