[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at c7ec3a7 [PowerPC] Implement Vector Extract Mask builtins in LLVM/Clang
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   c7ec3a7..a52173a  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to a52173a3e56553d7b795bcf3cdadcf6433117107.
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!