fix Makefile
fix Makefile

imotai/bfs,00k/ToyDFS,baidu/bfs,bluebore/dfs,baidu/bfs,yvxiang/dfs,myawan/bfs-1,bluebore/dfs,yvxiang/coverage_for_bfs,lylei/dfs,bluebore/bfs,baidu/bfs,myawan/bfs-1,myawan/bfs-1,yvxiang/dfs,linyvxiang/dfs,bluebore/dfs,yvxiang/coverage_for_bfs,linyvxiang/dfs,yvxiang/dfs,lylei/dfs,lylei/dfs,00k/ToyDFS,yvxiang/coverage_for_bfs,linyvxiang/dfs,yvxiang/dfs,myawan/bfs-1,baidu/bfs,imotai/bfs,bluebore/bfs,imotai/bfs,bluebore/bfs,yvxiang/coverage_for_bfs,lylei/dfs