Is there a way to configure npm-gyp to use gcc (as it appears to on Linux) on a Windows box?
This is not possible as described here.
UPDATE
An enhancement request has been submitted to the gyp team.
UPDATE
...but probably won't be acted upon. [comment]
I am not sure on how to configure gyp to use gcc, but I use npm install socket.io –msvs_version=2012 to install socket.io specifying it to use visual studio 2012 to build it (by default it will search for Visual Studio 2010).
http://www.kevgriffin.com/specifying-visual-studio-version-in-npm-installs/
Here's a more complete and up-to-date guide: https://github.com/TooTallNate/node-gyp/wiki/Visual-Studio-2010-Setup