fix-up patch: avoid new link error

Summary:
* src.mk (LIB_SOURCES): Add this file:
utilities/document/json_document_builder.cc
to avoid link errors.

Blame Rev: D33849

Test Plan: run "make"

Reviewers: ljin, igor.sugak, rven, sdong, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D34593

src.mk

@@ -92,6 +92,7 @@ LIB_SOURCES =                                                   \
   utilities/checkpoint/checkpoint.cc                            \
   utilities/compacted_db/compacted_db_impl.cc                   \
   utilities/document/document_db.cc                             \
+  utilities/document/json_document_builder.cc                   \
   utilities/document/json_document.cc                           \
   utilities/geodb/geodb_impl.cc                                 \
   utilities/leveldb_options/leveldb_options.cc                  \