[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 9b19400 [AArch64][GlobalISel] Make <8 x s16> and <16 x s8> legal types for G_SHUFFLE_VECTOR and G_IMPLICIT_DEF.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   9b19400..18df607  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 18df607dbeb41451f5842f46e9b7a67baf759d5e.
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!