[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at bc8be30 [X86][GlobalISel] Remove unneeded code for handling zext i8->16, i8->i64, i16->i64, i32->i64.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   bc8be30..c990455  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to c990455db91e52bd6b8ac9b68b06ef19f7239722.
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!