[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at c8b629a [Polly] Reuse LLVM's build rules for gtest/gmock
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   c8b629a..c70f0b9  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to c70f0b9d4a063df396bb63378963cedbaa357bb8.
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!