[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 54ce344 Refactor mlir-opt setup in a new helper function (NFC)
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   54ce344..22cbe40  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 22cbe40fa99795766f352c08a7c0748704c9d2d5.
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!