Ok, so I was lazy.
I wanted to save time so i just copied the bison.exe to my c:\osgeo4w\bin with was already set in my %PATH%. And it requires all these other files. So I changed the path in my CMake-GUI to point to the actual Bison.exe with access to the appropriate relative paths, and I made sure that it wasn't in a directory with spaces, and then reconfigured my CMake-GUI and regenerated my project, and its working now.