Recipes: make cwd default to slave_build

scripts/slave/recipes/chromium_trybot_legacy.expected/arm.json

Index: scripts/slave/recipes/chromium_trybot_legacy.expected/arm.json
diff --git a/scripts/slave/recipes/chromium_trybot_legacy.expected/arm.json b/scripts/slave/recipes/chromium_trybot_legacy.expected/arm.json
index 183740cfbf1a187840c029422779e1f127e57847..6a0360b22056016cf892de267733745234ffd3dd 100644
--- a/scripts/slave/recipes/chromium_trybot_legacy.expected/arm.json
+++ b/scripts/slave/recipes/chromium_trybot_legacy.expected/arm.json
@@ -28,6 +28,7 @@
       "src@HEAD",
       "--force"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "bot_update",
     "~followup_annotations": [
       "@@@STEP_TEXT@Some step text@@@",
@@ -75,6 +76,7 @@
       "[SLAVE_BUILD]/src/testing/buildbot/chromium_arm.json",
       "/path/to/tmp/json"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "read test spec",
     "~followup_annotations": [
       "@@@STEP_TEXT@path: testing/buildbot/chromium_arm.json@@@",
@@ -113,6 +115,7 @@
       "--properties",
       "{\"buildername\": \"linux_arm\", \"buildnumber\": 571, \"mastername\": \"tryserver.chromium.linux\", \"slavename\": \"TestSlavename\", \"target_platform\": \"linux\"}"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "get compile targets for scripts",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{}@@@",
@@ -142,6 +145,7 @@
       "[SLAVE_BUILD]/src/testing/buildbot/trybot_analyze_config.json",
       "/path/to/tmp/json"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "read filter exclusion spec",
     "~followup_annotations": [
       "@@@STEP_TEXT@path: 'testing/buildbot/trybot_analyze_config.json'@@@",
@@ -168,6 +172,7 @@
       "{\"files\": [\"foo.cc\"], \"targets\": [\"browser_tests\", \"base_tests\"]}",
       "/path/to/tmp/json"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "env": {
       "GYP_CROSSCOMPILE": "1",
       "GYP_DEFINES": "arm_float_abi=hard component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' target_arch=arm test_isolation_mode=archive use_goma=1"