Recipes: make cwd default to slave_build

scripts/slave/recipes/webrtc/chromium.expected/chromium_webrtc_fyi_Android_GN.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "chromium.webrtc.fyi",
       "--builder",
       "Android GN",
       "--slave",
       "TestSlavename",
       "--spec",
       "cache_dir = None\nsolutions = [{'custom_vars': {'googlecode_url': 'svn://svn-mirror.golo.chromium.org/%s', 'nacl_trunk': 'svn://svn-mirror.golo.chromium.org/native_client/trunk', 'sourceforge_url': 'svn://svn-mirror.golo.chromium.org/%(repo)s', 'webkit_trunk': 'svn://svn-mirror.golo.chromium.org/blink/trunk'}, 'deps_file': 'DEPS', 'managed': True, 'name': 'src', 'url': 'svn://svn-mirror.golo.chromium.org/chrome/trunk/src'}, {'deps_file': 'DEPS', 'managed': True, 'name': 'webrtc.DEPS', 'url': 'https://chromium.googlesource.com/chromium/deps/webrtc/webrtc.DEPS'}]\ntarget_os = ['android']",
       "--root",
       "src",
       "--revision_mapping_file",
       "{\"src\": \"got_revision\", \"src/native_client\": \"got_nacl_revision\", \"src/third_party/WebKit\": \"got_webkit_revision\", \"src/third_party/libjingle/source/talk\": \"got_libjingle_revision\", \"src/third_party/libvpx/source\": \"got_libvpx_revision\", \"src/third_party/webrtc\": \"got_webrtc_revision\", \"src/tools/swarming_client\": \"got_swarming_client_revision\", \"src/v8\": \"got_v8_revision\"}",
       "--output_json",
       "/path/to/tmp/json",
       "--revision",
       "src@HEAD",
       "--revision",
       "src/third_party/libjingle/source/talk@HEAD",
       "--revision",
       "src/third_party/webrtc@HEAD"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "bot_update",
     "~followup_annotations": [
       "@@@STEP_TEXT@Some step text@@@",
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"did_run\": true, @@@",
       "@@@STEP_LOG_LINE@json.output@  \"patch_failure\": false, @@@",
       "@@@STEP_LOG_LINE@json.output@  \"patch_root\": \"src\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"properties\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_libjingle_revision\": \"8e938c8836c7ed23d7fbcddf1dcc2abcb13667d7\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_libjingle_revision_cp\": \"refs/heads/master@{#134440}\", @@@",
@@ skipping 34 matching lines @@
       "@@@SET_BUILD_PROPERTY@got_libjingle_revision_cp@\"refs/heads/master@{#134440}\"@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[webrtc]/resources/cleanup_files.py",
       "[SLAVE_BUILD]/src/out"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "clean test output files"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil, sys, os\nshutil.rmtree(sys.argv[1], True)\nshutil.rmtree(sys.argv[2], True)\ntry:\n  os.remove(sys.argv[3])\nexcept OSError:\n  pass\nfor base, _dirs, files in os.walk(sys.argv[4]):\n  for f in files:\n    if f.endswith('.pyc'):\n      os.remove(os.path.join(base, f))\n",
       "[SLAVE_BUILD]/src/out/Debug/debug_info_dumps",
       "[SLAVE_BUILD]/src/out/Debug/test_logs",
       "[SLAVE_BUILD]/src/out/build_product.zip",
       "[SLAVE_BUILD]/src"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "clean local files",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",
       "@@@STEP_LOG_LINE@python.inline@import shutil, sys, os@@@",
       "@@@STEP_LOG_LINE@python.inline@shutil.rmtree(sys.argv[1], True)@@@",
       "@@@STEP_LOG_LINE@python.inline@shutil.rmtree(sys.argv[2], True)@@@",
       "@@@STEP_LOG_LINE@python.inline@try:@@@",
       "@@@STEP_LOG_LINE@python.inline@  os.remove(sys.argv[3])@@@",
       "@@@STEP_LOG_LINE@python.inline@except OSError:@@@",
       "@@@STEP_LOG_LINE@python.inline@  pass@@@",
       "@@@STEP_LOG_LINE@python.inline@for base, _dirs, files in os.walk(sys.argv[4]):@@@",
       "@@@STEP_LOG_LINE@python.inline@  for f in files:@@@",
       "@@@STEP_LOG_LINE@python.inline@    if f.endswith('.pyc'):@@@",
       "@@@STEP_LOG_LINE@python.inline@      os.remove(os.path.join(base, f))@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "env": {
       "GYP_CHROMIUM_NO_ACTION": "1",
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "gclient runhooks"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gn.py",
       "--root=[SLAVE_BUILD]/src",
       "gen",
       "//out/Release",
       "--args=symbol_level=1 is_debug=false target_os=\"android\" target_cpu=\"arm\" use_goma=true goma_dir=\"[BUILD]/goma\""
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "gn"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/compile.py",
       "--target",
       "Release",
       "--src-dir",
       "[SLAVE_BUILD]/src",
       "--build-tool",
       "ninja",
       "--compiler",
       "goma",
       "--goma-dir",
       "[BUILD]/goma",
       "--",
       "chrome_shell_apk"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "compile"
   }
 ]