Update Makefile to build correctly when building for 2nd/3rd/etc time.
Update Makefile to build correctly when building for 2nd/3rd/etc time.

wwezhuimeng/riak_search,amyvmiwei/riak,xuejianhai/riak_search,xuejianhai/riak,GabrielNicolasAvellaneda/riak,yangchengjian/riak,glickbot/riak,planobe/riak,planobe/riak,laurenrother/riak,basho/riak_search,elkingtonmcb/riak,wwezhuimeng/riak_search,basho/riak_search,authbox-lib/riak,DavidAlphaFox/riak,biddyweb/riak,basho/riak,xuejianhai/riak_search