only make liblevedb.a from included leveldb distribution
only make liblevedb.a from included leveldb distribution

wmorgan/leveldb-ruby,wmorgan/leveldb-ruby,wmorgan/leveldb-ruby,wmorgan/leveldb-ruby,assispedro/leveldb-ruby,assispedro/leveldb-ruby,assispedro/leveldb-ruby,assispedro/leveldb-ruby