[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 6484aa1 [clangd] Simplify relations deserialization loop, NFC.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   6484aa1..f9265de  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to f9265de8c634798b2ae8b4bdad7c2f5b7442115e.
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!