Compiling Shader Variants Taking Ages

Hi Guys,

I'm just building my project, and for some reason the 'compiling shader variants' is taking close to an hour to do. I mean fair play, it's a fairly large project, but for example for terrains I have a small park, with one grass texture and some of the built in unity trees.. That's it. It's compiling 6768 shader varients for 'Nature/SpeedTree'. Anyone have any idea why this is taking so long? Thanks!