Fix a printf format string (caught by clang but not GCC).

Change-Id: I665756615eef74b05ef92f5865d910f29ead0695
diff --git a/init/init.cpp b/init/init.cpp
index 579d0e7..e090620 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -366,7 +366,7 @@
     svc->flags |= SVC_RUNNING;
 
     if ((svc->flags & SVC_EXEC) != 0) {
-        INFO("SVC_EXEC pid %d (uid %d gid %d+%d context %s) started; waiting...\n",
+        INFO("SVC_EXEC pid %d (uid %d gid %d+%zu context %s) started; waiting...\n",
              svc->pid, svc->uid, svc->gid, svc->nr_supp_gids, svc->seclabel);
         waiting_for_exec = true;
     }