[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 5c98721 [SimplifyCFG] Remove unused check-prefixes
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   5c98721..f4f256f  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to f4f256fb7b7e6a7dcf64dc9f3f38ea9bd7a8f4ab.
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!