rocksdb: -Wno-portability

Signed-off-by: Sage Weil <sage@redhat.com>

diff --git a/src/rocksdb b/src/rocksdb
index c29e84505e81eb6de6c8feedaef26e08c1c5dc68..ab4d781db2f1ec6a47bd1ec6fe680fa9a8091e09 160000 (submodule)
--- a/src/rocksdb
+++ b/src/rocksdb
@@ -1 +1 @@
-Subproject commit c29e84505e81eb6de6c8feedaef26e08c1c5dc68
+Subproject commit ab4d781db2f1ec6a47bd1ec6fe680fa9a8091e09