For CWL support, symlink files into a working directory if in read-only imports.

def _symlink_to_workdir(data, key):
    """For CWL support, symlink files into a working directory if in read-only imports.
    """
    orig_file = tz.get_in(key, data)
    if orig_file and not orig_file.startswith(dd.get_work_dir(data)):
        variantcaller = genotype.get_variantcaller(data, require_bam=False)
        if not variantcaller:
            variantcaller = "precalled"
        out_file = os.path.join(dd.get_work_dir(data), variantcaller, os.path.basename(orig_file))
        utils.safe_makedir(os.path.dirname(out_file))
        utils.symlink_plus(orig_file, out_file)
        data = tz.update_in(data, key, lambda x: out_file)
    return data