[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at f980ed4 [libcxx] Remove the 'availability' Lit feature
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   f980ed4..8ecc852  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 8ecc8520bc5bc20ae00c13e5ae13f8edbb80642e.
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!