webrtc: run tests in the checkout directory

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

Index: scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_linux_memcheck.json
diff --git a/scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_linux_memcheck.json b/scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_linux_memcheck.json
index 1b5bbbfe1298342ad1c2bb5c5c1e22b023854f27..b2424ec00916bfb9b488e7196df413855c042dff 100644
--- a/scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_linux_memcheck.json
+++ b/scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_linux_memcheck.json
@@ -260,7 +260,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "audio_decoder_unittests"
   },
   {
@@ -292,7 +292,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "common_audio_unittests"
   },
   {
@@ -324,7 +324,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "common_video_unittests"
   },
   {
@@ -356,7 +356,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "modules_tests"
   },
   {
@@ -388,7 +388,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "modules_unittests"
   },
   {
@@ -420,7 +420,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "peerconnection_unittests"
   },
   {
@@ -452,7 +452,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "rtc_media_unittests"
   },
   {
@@ -484,7 +484,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "rtc_pc_unittests"
   },
   {
@@ -516,7 +516,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "rtc_unittests"
   },
   {
@@ -548,7 +548,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "system_wrappers_unittests"
   },
   {
@@ -580,7 +580,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "test_support_unittests"
   },
   {
@@ -612,7 +612,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "tools_unittests"
   },
   {
@@ -644,7 +644,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "video_engine_tests"
   },
   {
@@ -676,7 +676,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "voice_engine_unittests"
   },
   {
@@ -708,7 +708,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "xmllite_xmpp_unittests"
   },
   {
@@ -740,7 +740,7 @@
       "--tool",
       "memcheck"
     ],
-    "cwd": "[BUILDER_CACHE]/Linux_Memcheck",
+    "cwd": "[BUILDER_CACHE]/Linux_Memcheck/src",
     "name": "webrtc_nonparallel_tests"
   },
   {