[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 22d10b8 [CostModel] remove cost-kind predicate for vector reduction costs
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   22d10b8..6f9d84b  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 6f9d84bb26f15845e984170be40f7c1383425eea.
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!