[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at af0d607 [clang-tidy] Fix an abseil-redundant-strcat-calls crash on 0-parameter StrCat().
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   af0d607..6795984  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 6795984a47dfd2da4f451ad86a99021d6c9f85b5.
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!