def LCGInfoName(platform):
    """
    Return the name of the file containing the list of externals in an LCG
    relese.

    >>> LCGInfoName('x86_64-slc6-gcc49-opt')
    'LCG_externals_x86_64-slc6-gcc49-opt.txt'
    """
    return 'LCG_externals_{0}.txt'.format(platform)
