[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at f2c25c7 [CostModel] remove cost-kind predicate for some vector reduction costs
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   f2c25c7..63ba82e  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 63ba82ed00ffe3e5d5f4ce907c4523d8d980fc8a.
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!