[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 557db6f Reland D84057 [PGO][PGSO] Remove a temporary flag used for gradual rollout.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   557db6f..dab898f  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to dab898f9ab62275f55eb2a7e76ea0cd01696f68e.
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!