[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 952dc7f [gn build] Port 7fff1fbd3ce
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   952dc7f..3d54976  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 3d54976a704327aea8de85f7b2c36172e42100d9.
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!