[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at f6f3402 [ELF] Add documentation for --warn-backrefs: a GNU ld compatibility checking tool (and lesser of layering detection)
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   f6f3402..7d1ed69  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 7d1ed69c8aad00f3ba1e917da54508489de6d610.
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!