[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at ccf1260 [InstCombine] Add tests for X shift (A srem B) -> X shift (A and B-1) pow2 nonuniform constant vectors
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   ccf1260..dcd9be4  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to dcd9be43e5c7c371991bc89f617c6cfe0110c82d.
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!