[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 1aa8e6a [SDag] SimplifyDemandedBits: simplify to FP constant if all bits known
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   1aa8e6a..20cfd5f  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 20cfd5fa3362c71d0184639decf5c2acb743e4e6.
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!