[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at d720ba1 [X86][SSE] SimplifyDemandedVectorEltsForTargetNode - add SSE shift multiple use handling
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   d720ba1..06b9058  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 06b90586a4c99ea44af03d7d722e96941164d122.
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!