Working IDEA 15 build vs broken Ant build

Hi folks,

How can I get the exact command line and options that IDEA uses to build the project so that I can duplicate it in the ant scripts (javac2 task)?  

I've got the Haxe plugin building and working from within IDEA v15, using the Build->Make/Rebuild Project.  However, using ant from within IDEA or the command line, I'm getting compiler errors (NPE in the compiler itself) -- compiling the exact same sources.  

BTW, the ant script that IDEA creates doesn't work at all, it just errors out trying to annotate forms.  Beside that, it appears to use the same ant task and options that I do.

Any ideas are appreciated.  Sources are at http://github.com/tivo/intellij-haxe  v15Build branch, if anybody wants to take a look.

Thanks,

-Eric