[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 50dfa19 [CostModel] remove cost-kind predicate for FP add/mul vector reduction costs
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   50dfa19..d69ada3  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to d69ada30e23f1b226daeee3a9b13826e1e368ede.
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!