Make sure we get the right nix-store, too.

def _nix_collect_garbage():
    '''
    Make sure we get the right nix-store, too.
    '''
    nixhome = os.path.join(os.path.expanduser('~{0}'.format(__opts__['user'])), '.nix-profile/bin/')
    return [os.path.join(nixhome, 'nix-collect-garbage')]