[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at ff5758f AMDGPU/GlobalISel: Add some bitcast tests
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   ff5758f..1922bf1  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 1922bf12e1f3f228c0f57b27c796ebea4a50c358.
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!