[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at f9ca205 [libc++] Move the default site config template alongside other config files
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   f9ca205..1013468  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 1013468fe6f513ba6a1770e7043506bd0f026ffe.
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!