Some time ago I emulated the Raspberry Pi following this article, but this approach has several problems:
If you want to run a Raspberry Pi 2 build bot or something similar you should take a look at running Qemu in user/static mode. I tried this using Linux in a virtual machine, it's quite fast compared to Qemu system emulation. Unfortunately it only emulates the CPU so you won't be able to test games or Wayland/Weston.
I was able to build a kernel for my Pi 2 in roughly a hour using this method.