[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at ab4e1be [InstCombine] Add a test for folding freeze into phi; NFC
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   ab4e1be..3bbf3e0  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 3bbf3e026d3c692966583075ae6d12c4575e9d72.
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!