Even I got the same error, I tried installing "ant" but it did not work because 'bin' directory was missing over there. I tried something else, I uninstalled the version of pig.0.16.0 I was using and installed the latest version pig.0.17.0.
After installing, I put down all the directories present inside it and then installed ant to build the pig. Because the Pig-script file, the pig, is located in the bin directory. Make sure you change all the necessary configuration in the .bashrc file according to your pig version.