[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at e3475f5 [PowerPC] Add builtins for xvtdiv(dp|sp) and xvtsqrt(dp|sp).
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   e3475f5..f5fe7ab  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to f5fe7abe8a8c8150b7b305bae963b429f15ea217.
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!