Remove a dead variable from ldmd. (It used to be used to pass an extra -help to ldc when no files were specified, but we handle that in ldc itself now)

module c;

void main()
{
    ushort a = 0xFFF0;
    ushort b = 0x0FFF;
    auto t = a & b;
    a &= b;
    assert(t == a);
}