[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 3cb8347 [APIntTest] Extend extractBits to check 'lshr+trunc' pattern for each case as well.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   3cb8347..6b441ca  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 6b441ca523cd6be9475106408a60989ad1f5ae55.
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!