[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at fa5f945 [lld-macho] cleanup unimplemented-option warnings
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   fa5f945..881aba7  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 881aba7071c6e4cc2417e875ca5027ec7c0a92a3.
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!