[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at f92e0d9 [VE] Optimize trunc related instructions
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   f92e0d9..f4ba7a1  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to f4ba7a100a56b63f9b3eac709ecea9f514d90c00.
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!