[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at a5bb247 [llvm-reduce] Create returns with undef values for non-void functions.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   a5bb247..eb2a405  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to eb2a405c181c9833eb8676d147619b8c893dc6fa.
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!