Made a video/guide and blog post about installing llvm-svn and mesa-git on Arch with and without libglvnd:

https://www.youtube.com/watch?v=HeOLIVkO3tw

https://www.gloriouseggroll.tv/arch-linux-installing-and-compiling-mesa-git-and-llvm-svn-with-and-without-libglvnd/