[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at d1b2a52 [clang-tidy] Add signal-handler-check for SEI CERT rule SIG30-C
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   d1b2a52..42f1916  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 42f19166405878459e27bf682ad38b8f1ac43d0a.
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!