CHeck boost_1_57_0.tar.gz Before Remove (#891)
CHeck boost_1_57_0.tar.gz Before Remove (#891)

ensure the boost_1_57_0.tar.gz exists before remove action.
bluebore/dfs,bluebore/bfs,baidu/bfs,baidu/bfs,bluebore/bfs,bluebore/dfs,bluebore/bfs,baidu/bfs,baidu/bfs,bluebore/dfs