Recipes: make cwd default to slave_build

scripts/slave/recipe_modules/chromium/example.expected/basic_out_dir.json

Index: scripts/slave/recipe_modules/chromium/example.expected/basic_out_dir.json
diff --git a/scripts/slave/recipe_modules/chromium/example.expected/basic_out_dir.json b/scripts/slave/recipe_modules/chromium/example.expected/basic_out_dir.json
index 96f0fba768310e17cf79d824bc89d0bf296a429c..4f3e4d53092c0a628a1bd4a70932cd69c5690f65 100644
--- a/scripts/slave/recipe_modules/chromium/example.expected/basic_out_dir.json
+++ b/scripts/slave/recipe_modules/chromium/example.expected/basic_out_dir.json
@@ -21,6 +21,7 @@
       "--revision",
       "src@HEAD"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "bot_update",
     "~followup_annotations": [
       "@@@STEP_TEXT@Some step text@@@",
@@ -67,6 +68,7 @@
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "env": {
       "GYP_CROSSCOMPILE": "1",
       "GYP_DEFINES": "OS=android component=static_library fastbuild=1 gomadir='[BUILD]/goma' target_arch=arm use_goma=1",
@@ -82,6 +84,7 @@
       "[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@@@",
@@ -104,6 +107,7 @@
       "--properties",
       "{\"buildername\": \"Android Builder (dbg)\", \"buildnumber\": \"77457\", \"mastername\": \"chromium.linux\", \"slavename\": \"build1-a1\", \"target_platform\": \"android\"}"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "get compile targets for scripts",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{}@@@",
@@ -130,6 +134,7 @@
       "--",
       "All"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },