Adds the dependency calls from the specified executable instance
    to the results dictionary.

def _exec_callers(xinst, result):
    """Adds the dependency calls from the specified executable instance
    to the results dictionary.
    """
    for depkey, depval in xinst.dependencies.items():
        if depval.target is not None:
            if depval.target.name in result:
                if xinst not in result[depval.target.name]:
                    result[depval.target.name].append(xinst)
            else:
                result[depval.target.name] = [xinst]

    for xname, xvalue in xinst.executables:
        _exec_callers(xvalue, result)