That's the error. Assuming you don't have that library installed, the solution is probably as simple as installing it. But if you already have that library installed, then we need to work out why it's not being found.
Re: Can't Install GD
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I feel dumb; when I read that I thought it was just a flag for another command and didn't think it was a missing library. A google search later and I installed xpm and then the package; no problems. I guess I just needed syphilis. Thanks!