Porting native ruby gems to Win32 is a bitch. I have been using ruby-xslt for our XSLT needs on OS X for a while now and finally had to port it to Windows to support our minority of Windows developers.
Here is my advice for if you have to do this sort of thing:
Download the Windows SDK – turns out you can download the Windows development tools for free now. The web install wasted many hours of my time getting clogged and refusing to install and it would have been faster to just download the ISO in the first place. You don’t need all the .Net stuff.
Try to get rid of any shell scripts in the gem build process. There was a little shell to build the arguments to the linker to include the xslt libraries for example. I wasted a bunch of time trying to get it to run in the build process somehow when the real best answer was to look at the output in cygwin and put the equivalent flags straight into my Makefile.
There is a magic thing you have to do with manifests that I don’t even pretend to understand:
mt.exe -manifest my_lib_name.so.manifest -outputresource:my_lib_name.so;2
These blog posts by Al Hoang explain a lot.
You probably have to include msvcr80.dll with your thing which is installed and used by the SDK.
Replace non-portable library calls with portable calls back into Ruby, not with Windows native calls. There were a bunch of POSIX file calls in the ruby-xslt library for opening and reading libraries. Those kinds of things are really easy to replace by just calling methods on File from C.
I’d like to get this all cleaned up and made available with ruby-xslt so it can be used straight from the gem by Windows users. But it is extra work and gem install stuff is confusing and weird. Email me if ruby-xslt for Windows is something you are looking for though and maybe I will try to put some effort into it.