[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at b0512ee [clang][NFC] Add a test for __attribute__((flag_enum)) with an unnamed enumeration.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   b0512ee..ab4e1be  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to ab4e1be7ab3f1a1e7b78316b5b1929963e0e3bce.
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!