[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at a6436b0 [yaml2obj] - Make the 'Machine' key optional.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   a6436b0..455d5a8  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 455d5a8a065b4b93df11d1696dc1546c403465a5.
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!