build: match upstream build change

Author: theuni

src/Makefile.am

@@ -31,7 +31,7 @@ LIBBITCOIN_UTIL=libbitcoin_util.a
 LIBBITCOIN_CRYPTO=crypto/libbitcoin_crypto.a
 LIBBITCOINQT=qt/libbitcoinqt.a
 LIBSECP256K1=secp256k1/libsecp256k1.la
-LIBUNIVALUE=univalue/lib/libunivalue.la
+LIBUNIVALUE=univalue/libunivalue.la
 
 $(LIBSECP256K1): $(wildcard secp256k1/src/*) $(wildcard secp256k1/include/*)
 	$(AM_V_at)$(MAKE) $(AM_MAKEFLAGS) -C $(@D) $(@F)