webrtc: use correct cwd for running tests

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

Index: scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_linux_rel.json
diff --git a/scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_linux_rel.json b/scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_linux_rel.json
index 931b3eb9ce5cbe6f55c7f74982be8f5b874c96a2..28c9290f395514f54d21e9b8af733ebff23e0e70 100644
--- a/scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_linux_rel.json
+++ b/scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_linux_rel.json
@@ -262,6 +262,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/audio_decoder_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "audio_decoder_unittests"
   },
   {
@@ -287,6 +288,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/common_audio_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "common_audio_unittests"
   },
   {
@@ -312,6 +314,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/common_video_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "common_video_unittests"
   },
   {
@@ -337,6 +340,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/modules_tests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "modules_tests"
   },
   {
@@ -362,6 +366,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/modules_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "modules_unittests"
   },
   {
@@ -387,6 +392,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/peerconnection_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "peerconnection_unittests"
   },
   {
@@ -412,6 +418,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/rtc_media_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "rtc_media_unittests"
   },
   {
@@ -437,6 +444,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/rtc_pc_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "rtc_pc_unittests"
   },
   {
@@ -462,6 +470,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/rtc_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "rtc_unittests"
   },
   {
@@ -487,6 +496,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/system_wrappers_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "system_wrappers_unittests"
   },
   {
@@ -512,6 +522,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/test_support_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "test_support_unittests"
   },
   {
@@ -537,6 +548,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/tools_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "tools_unittests"
   },
   {
@@ -562,6 +574,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/video_engine_tests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "video_engine_tests"
   },
   {
@@ -587,6 +600,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/voice_engine_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "voice_engine_unittests"
   },
   {
@@ -612,6 +626,7 @@
       "[BUILDER_CACHE]/linux_rel/src/out/Release/xmllite_xmpp_unittests",
       "--"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "xmllite_xmpp_unittests"
   },
   {
@@ -636,6 +651,7 @@
       "--revision=f27fede2220bcd326aee3e86ddfd4ebd0fe58cb9",
       "webrtc_nonparallel_tests"
     ],
+    "cwd": "[BUILDER_CACHE]/linux_rel",
     "name": "webrtc_nonparallel_tests"
   },
   {