[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 455ca0e [SLP] Allow reordering of vectorization trees with reused instructions.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   455ca0e..1909b6a  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 1909b6ac0dbc2f1306103a5ea7f5e59f2232b133.
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!