[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 2878ecc [StackProtector] Fix crash with vararg due to not checking LocationSize validity.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   2878ecc..5b354d2  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 5b354d204d0952a6dd39e41fb41b51414bff5f0b.
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!