A little preliminary building must be done to download libraries and build generated code, to do so:

Windows:

Open the command line.

cd to the root of the daffodil git repository. Note the default is "C:\Users\UserName\git\dfdl".

Run the following command:

sbt update-classifiers

Linux:

Open the terminal.

cd to the root of the daffodil git repository.

Run the following command:

sbt update-classifiers