1. Use ant (gradle is experimental)
2. Ant 1.7.1 causes trouble on ubuntu (see issue 195: http://code.google.com/p/mockito/issues/detail?id=195)
3. If it does not build let me know (but be gentle because it will be very embarassing for me and I will quit coding and open a grocery. Seriously). 
4. CI server is here: http://hudson.ramfelt.se/job/Mockito/ If it builds there then it must build on your box.