[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 32556a9 [ARM] Remove more unused check prefixes, NFC
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   32556a9..5a2febb  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 5a2febb31af7e3ee2f6d1a3495c6ccbc7c7031b5.
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!