Building the XNU kernel on Mac OS X Sierra

From version to version, I always love to play around with the kernel. And it has always been a great lack in guides and documentation on how to build Mac OSX's kernel, XNU. For those of you that already have tried compiling XNU for Mac OSX 10.12 (Sierra), you probably noticed that earlier build guides like ssen's blog - Building xnu for OS X 10.11 El Capitan don't work anymore. However, many thanks to ssen to put in time to write a guide.The problem is that Apple introduced something named Circular dependency with the libdispatch library and the kernel headers. So the order of the build process just got really important.