[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 1e66e72 [RISCV] Merge the pipeline models for Rocket
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   1e66e72..276f68e  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 276f68eace7c27f6805d69a30a4b2f186e42c56c.
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!