build.xml:61: Specify at least one source

http://eason982.blogspot.com/2007/11/buildxml61-specify-at-least-one-source.html

nutch 版本：nutch-0.9 In cygwin shell
問題： 用ant直接compile遇到 build.xml:61: Specify at least one source 的error
solution: 把下面的codes 註解掉就解決