[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 276f68e Revert "Add a static_assert confirming that DiagnosticBuilder is small"
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   276f68e..1c45220  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 1c45220028a8aa39ad2f26c8c3c6234d1a816086.
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!