[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at e4e5c42 [X86][SSE] isTargetShuffleEquivalent - ensure shuffle inputs are the correct size.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   e4e5c42..2ccbf3d  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 2ccbf3dbd5bac9d4fea8b67404b4c6b006d4adbe.
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!