[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 99e865b [TargetRegisterInfo] Add a couple of target hooks for the greedy register allocator
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   99e865b..196e2f9  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 196e2f97b714bb535a39a2daa949e523c21c0269.
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!