[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 324a532 [InstCombine] propagate 'nsw' on pointer difference of 'inbounds' geps (PR47430)
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   324a532..f980ed4  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to f980ed4184f9d9139961e21739d7692ea86b0ccf.
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!