[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 795e4ee [NFC] Move functon from IndVarSimplify to SCEV
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   795e4ee..c58dfbd  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to c58dfbdc818275dd0e8f34939a95da546c49cdf6.
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!