webrtc: use correct cwd for running tests

scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_mac64_debug.json

Index: scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_mac64_debug.json
diff --git a/scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_mac64_debug.json b/scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_mac64_debug.json
index 26ad06d26896160f62a866b3caa067fbfc4a99a1..737eb7b1b5b8829df9e5e2454c0fd3a8502a1529 100644
--- a/scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_mac64_debug.json
+++ b/scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_mac64_debug.json
@@ -273,6 +273,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/audio_decoder_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "audio_decoder_unittests"
   },
   {
@@ -297,6 +298,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/common_audio_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "common_audio_unittests"
   },
   {
@@ -321,6 +323,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/common_video_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "common_video_unittests"
   },
   {
@@ -345,6 +348,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/modules_tests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "modules_tests"
   },
   {
@@ -369,6 +373,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/modules_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "modules_unittests"
   },
   {
@@ -393,6 +398,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/peerconnection_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "peerconnection_unittests"
   },
   {
@@ -417,6 +423,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/rtc_media_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "rtc_media_unittests"
   },
   {
@@ -441,6 +448,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/rtc_pc_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "rtc_pc_unittests"
   },
   {
@@ -465,6 +473,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/rtc_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "rtc_unittests"
   },
   {
@@ -489,6 +498,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/system_wrappers_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "system_wrappers_unittests"
   },
   {
@@ -513,6 +523,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/test_support_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "test_support_unittests"
   },
   {
@@ -537,6 +548,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/tools_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "tools_unittests"
   },
   {
@@ -561,6 +573,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/video_engine_tests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "video_engine_tests"
   },
   {
@@ -585,6 +598,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/voice_engine_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "voice_engine_unittests"
   },
   {
@@ -609,6 +623,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/xmllite_xmpp_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "xmllite_xmpp_unittests"
   },
   {
@@ -633,6 +648,7 @@
       "[BUILDER_CACHE]/Mac64_Debug/src/out/Debug/libjingle_peerconnection_objc_test.app/Contents/MacOS/libjingle_peerconnection_objc_test",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "libjingle_peerconnection_objc_test"
   },
   {
@@ -659,6 +675,7 @@
       "--revision=f27fede2220bcd326aee3e86ddfd4ebd0fe58cb9",
       "webrtc_nonparallel_tests"
     ],
+    "cwd": "[BUILDER_CACHE]/Mac64_Debug",
     "name": "webrtc_nonparallel_tests"
   },
   {