[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at adfaeec [JumpThreading] Rename thread-prob-3.ll to thread-prob-1.ll (NFC)
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   adfaeec..624fc63  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 624fc63a0510d77dc9f08099aa1d2d9f1996775c.
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!