[Docs] Adds new section to User Guides page
[Docs] Adds new section to User Guides page

Adds a section to the User Guides page for articles related to building, packaging, and distributing LLVM. Includes sub-sections for CMake, Clang, and Docker.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@373113 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm