[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at e28c589 [AArch64][GlobalISel] Make <8 x s8> integer arithmetic ops legal.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   e28c589..5402d11  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 5402d11b1d8853ff10417b0f8d32edde3f4a51c0.
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!