Bug 967006 - Fix Clang build failure in nICEr. r=abr

media/mtransport/third_party/nICEr/src/stun/stun_build.h

@@ -55,7 +55,8 @@ int nr_stun_build_req_no_auth(nr_stun_client_stun_binding_request_params *params
 
 
 typedef struct nr_stun_client_stun_keepalive_params_ {
-#ifdef WIN32  // silly VC++ gives error if no members
+#if defined(WIN32) || defined(__clang__)
+    // VC++ and clang give error and warning respectively if no members
     int dummy;
 #endif
 } nr_stun_client_stun_keepalive_params;