Bugfix: The var is LIBUNIVALUE,not LIBBITCOIN_UNIVALUE

Author: luke-jr

src/Makefile.bench.include

@@ -14,7 +14,7 @@ bench_bench_bitcoin_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 bench_bench_bitcoin_LDADD = \
   $(LIBBITCOIN_SERVER) \
   $(LIBBITCOIN_COMMON) \
-  $(LIBBITCOIN_UNIVALUE) \
+  $(LIBUNIVALUE) \
   $(LIBBITCOIN_UTIL) \
   $(LIBBITCOIN_CRYPTO) \
   $(LIBLEVELDB) \