[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 707c3d4 [AMDGPU][RegAlloc][SplitKit] Pre-commit test for D88821
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   707c3d4..007dd12  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 007dd12d546814977519b33ca38b1cc8b31fee26.
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!