Ant: build.xml does not exist

Hello,
I’m trying to make a packaging of my ETC1 android project but the problem is that I have this error:
UATHelper: Packaging (Android (ETC1)): ERROR: cmd.exe failed with args /c “F:/Download/apache-ant-1.8.2/bin/ant.bat” debug -Djava.source=1.7 -Djava.target=1.7

I searched and found that Ant gave me this hour:
build.xml does not exist

Can you help me solve my problem?
thank you