[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 2b9a708 [gn build] Port 6a89cb8136f
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   2b9a708..ee7d315  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to ee7d315cd939017db6ca6db4827b579e8bd85ec1.
CMake Error at CMakeLists.txt:3 (cmake_minimum_required):
  CMake 3.13.4 or higher is required.  You are running version 3.7.1


-- Configuring incomplete, errors occurred!