You'll need to make a new .sublime-build file, which specifies ant. I'd imagine it'd look something like:
Save this as Ant.sublime-build under %APPDATA%/Sublime Text X/Packages/User (assuming you're using windows), restart Sublime Text X, and there will be an 'Ant' option in the build systems menu.
If "ant" isn't in your path, then you can modify the cmd to include the full path to it.
The file_regex works that same as lineNumberRegex in Sublime Text 1.x (docs for which are at sublimetext.com/docs/build), except it also supports an optional 4th capture for the error message, which will be displayed in the status bar.