cURL on ESXi 5.0?

I would strongly advise you NOT to do this at all, the whole point of VMWare dropping ESX in favour of an ESXi-only product set was to discourage 'in-host' additions and tinkering. They want us to just build our hosts and leave them alone, something I personally understand, adhere to and encourage.

I don't know what you're actually trying to achieve but I'm sure you could get to that point using supported tools thus leaving your hosts to do what they do unfettled.

You shouldn't try to run a binary like that on ESXi. It's not meant for that. Are you trying to download something directly to ESXi? If so, please try using wget. It's built-in.

Usage: wget [-c|--continue] [-s|--spider] [-q|--quiet] [-O|--output-document file]
        [--header 'header: value'] [-Y|--proxy on/off] [-P DIR]
        [-U|--user-agent agent] url

Retrieve files via HTTP or FTP

Options:
        -s      Spider mode - only check file existence
        -c      Continue retrieval of aborted transfer
        -q      Quiet
        -P      Set directory prefix to DIR
        -O      Save to filename ('-' for stdout)
        -U      Adjust 'User-Agent' field
        -Y      Use proxy ('on' or 'off')