Fix gn build of stun_prober

The common_config must be included in order for LOG to work within Chrome.

Otherwise you get compile errors... See https://codereview.chromium.org/2300923002/

TBR=pthatcher@webrtc.org

Review URL: https://codereview.webrtc.org/2305643002 .

Cr-Commit-Position: refs/heads/master@{#14020}

webrtc/p2p/BUILD.gn

@@ -168,6 +168,7 @@ executable("stun_prober") {
     "stunprober/main.cc",
   ]
 
+  configs += [ "..:common_config" ]
   if (!build_with_chromium && is_clang) {
     # Suppress warnings from Chrome's Clang plugins.
     # See http://code.google.com/p/webrtc/issues/detail?id=163 for details.