[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at bb8f258 [libc] Add implementations of ldexp[f|l].
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   bb8f258..b13415b  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to b13415b59b1fbb01da0914678018c7e0eefa3291.
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!