[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 160c133 [gn build] Port 79298a50670
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
Current branch master is up to date.
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!