Not to build forward_iterator_bench now

Summary: forward_iterator_bench is not stable enough for build. Remove it for now.

Test Plan: Build it with both of CLANG and non-CLANG and make sure it builds.

Reviewers: rven, kradhakrishnan, anthony, yhchiang, igor, IslamAbdelRahman

Reviewed By: igor, IslamAbdelRahman

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D50991

Makefile

@@ -345,7 +345,8 @@ TOOLS = \
 	rocksdb_dump \
 	rocksdb_undump
 
-BENCHMARKS = db_bench table_reader_bench cache_bench memtablerep_bench forward_iterator_bench
+# TODO: add back forward_iterator_bench, after making it build in all environemnts.
+BENCHMARKS = db_bench table_reader_bench cache_bench memtablerep_bench
 
 # if user didn't config LIBNAME, set the default
 ifeq ($(LIBNAME),)
@@ -986,9 +987,6 @@ ldb_cmd_test: tools/ldb_cmd_test.o $(LIBOBJECTS) $(TESTHARNESS)
 ldb: tools/ldb.o $(LIBOBJECTS)
 	$(AM_LINK)
 
-forward_iterator_bench: db/forward_iterator_bench.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(AM_LINK)
-
 #-------------------------------------------------
 # make install related stuff
 INSTALL_PATH ?= /usr/local

src.mk

@@ -190,7 +190,6 @@ TEST_BENCH_SOURCES =                                                    \
   db/db_compaction_filter_test.cc                                       \
   db/db_compaction_test.cc                                              \
   db/db_dynamic_level_test.cc                                           \
-  db/forward_iterator_bench.cc                                          \
   db/db_inplace_update_test.cc                                          \
   db/db_log_iter_test.cc                                                \
   db/db_universal_compaction_test.cc                                    \