[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 91671e1 [mlir] Fix -Wunused-variable in -DLLVM_ENABLE_ASSERTIONS=off build after D85869
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   91671e1..5502cfa  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 5502cfa091e0f6b35a6d96435b2ec15a43a324eb.
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!