[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at e902269 [NFC][Regalloc] Type 2 statics in terms of Register
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   e902269..de6f3d1  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to de6f3d1c71332b2c0ba00a2792c02be72b245d22.
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!