[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at ecac5c2 [X86][AVX] lowerShuffleWithPERMV - adjust binary shuffle masks to account for widening on non-VLX targets
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   ecac5c2..8c386c9  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 8c386c94749a78392fd763f8449ca3e55f030ffd.
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!