[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 7bae2bc [LoopUtils] Only verify SE in builds with assertions.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   7bae2bc..8b08fa0  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 8b08fa0103c8d8e624b19fad5a5006e7a783ecb7.
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!