Build node_g for debugging

[polotek]

Here's a patch to add --debug to the configuration. I think it should be on by default. Could also add a flag to turn it on.

http://gist.github.com/371887

[polotek]

Also add the --prefix to the install job. Right now if you run it, it tries to reinstall in the default location.

[creationix]

I just say this ticket. I fixed both these issues yesterday. I don't want to add --debug for the regular releases, they're meant for my production box. In fact that was the whole point of making nvm, I'm still not convinced of the value of having the head version in here.