[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 86a480e [AMDGPU] Add simplification/combines for llvm.amdgcn.fmul.legacy
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   86a480e..ff87c4d  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to ff87c4d3e773ae89ae62af20941339f0f252dafd.
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!