[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at dd63506 [lldb/cmake] Fix linking of lldbSymbolHelpers for 9cb222e7
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   dd63506..c9455d3  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to c9455d3c579292e7ae5b7559ad0302d459e69a95.
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!