[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 251dd7c [x86] add cost overrides for mul with overflow
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   251dd7c..84e8257  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 84e8257937ec6a332aa0b688f4dce57016516ffd.
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!