[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 8ea7ef8 [ThinLTO] Relax thinlto_embed_bitcode.ll check
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   8ea7ef8..c913f6d  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to c913f6dce69513b430f705d5a1f4e745f5d0a27e.
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!