[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 79b44a4 [YAMLTraits] Fix mapping <none> value that followed by comments.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   79b44a4..d4fbbab  master     -> origin/master
Auto packing the repository for optimum performance. You may also
run "git gc" manually. See "git help gc" for more information.
First, rewinding head to replay your work on top of it...
Fast-forwarded master to d4fbbab2e494a59480096a257136ed2b75d07e87.
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!