[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 4ccc388 [AMDGPU][CostModel] Add f16, f64 and contract cases to fused costs estimation.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   4ccc388..05df9cc  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 05df9cc70367a60cb34bee773389ab2522984f8b.
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!