[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at bb448a2 [SLP] Add test where reduction result is used in PHI.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   bb448a2..c7d4aa7  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to c7d4aa711ab7981358b5e17e56f1fb6f7f585ac1.
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!