Use the build system rules to compile the .proto files.

Change-Id: If5f98e50a40fdca88c69e889e952adc9f4170d77
diff --git a/mock-ril/src/cpp/requests.cpp b/mock-ril/src/cpp/requests.cpp
index 3e967af..acc4fc4 100644
--- a/mock-ril/src/cpp/requests.cpp
+++ b/mock-ril/src/cpp/requests.cpp
@@ -20,7 +20,7 @@
 #include <telephony/ril.h>
 
 
-#include "ril.pb.h"
+#include "hardware/ril/mock-ril/src/proto/ril.pb.h"
 
 #include "logging.h"
 #include "js_support.h"