There have been a lot of errors regarding building Spigot using the BuildTools jar. Most of these issues that I've seen over the last day are repeat issues, and can be easily resolved by doing one of four things. 1) Reviewing the BuildTools Wiki page. It even has common errors at the bottom! 2) Checking the Tickets for any issues similar to yours. (Yes, it requires an account) 3) Going on IRC and asking for help. (You'll be amazed how much quicker it is, both for you and us) 4) Looking through previous posts on here before making your post. (It's annoying to have to answer dupe posts). So please, look before you post, chances are your issue has been noticed and a working solution exists.