zkDSL compiler bug (duplicated files)

[TomWambsgans]

Goal = make this pass:

#[test]
fn test_num_files() {
    let expected_num_files = 3; // program_6.snark imports foo.snark and bar.snark
    let manifest_dir = env!("CARGO_MANIFEST_DIR");
    let path = format!("{manifest_dir}/tests/program_6.snark");
    let bytecode = compile_program(&ProgramSource::Filepath(path));
    assert_eq!(bytecode.filepaths.len(), expected_num_files);
    assert_eq!(bytecode.source_code.len(), expected_num_files);
}