[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 462b356 [libc][obvious] Add the new ctype.h target to the list of x86_64 headers.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   462b356..3044092  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 30440924d48cdcbdef1dd7b2791171d821a859ae.
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!