[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at b81c57d [ARM][LowOverheadLoops] Allow tail predication on predicated instructions with unknown lane
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   b81c57d..cd89f5c  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to cd89f5c91b4bad90278a59865fc06a75211589a1.
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!