Build: prepare Error reading project file ext/ant-javacard/build.xml

[PixsaOJ]

Error while running ant.sh

➜  openjavacard-ndef git:(master) ✗ ./ant.sh
Buildfile: /home/pixsa/Desktop/Job/Cnick/openjavacard-ndef/build.xml

prepare:

BUILD FAILED
/home/pixsa/Desktop/Job/Cnick/openjavacard-ndef/build.xml:20: The following error occurred while executing this line:
Error reading project file PATH/openjavacard-ndef/ext/ant-javacard/build.xml: PATH/openjavacard-ndef/ext/ant-javacard/build.xml

Total time: 0 seconds

This makes sense, because ext/ant-javacard/build.xml file is not present.
How should I generate it?

[PixsaOJ]

I tried to fix it and now it goes in loop.

/openjavacard-ndef/ext/ant-javacard/build.xml:20: Basedir openjavacard-ndef/ext/ant-javacard/ext/ant-javacard  does not exist

Almost like it cannot start from the relative directory of project root.

[PixsaOJ]

Make sure all submodules inside ext folder are downloaded guys.