[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 907d799 [AMDGPU] Cleanup memory legalizer interfaces
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   907d799..dc128e5  master     -> origin/master
Auto packing the repository for optimum performance. You may also
run "git gc" manually. See "git help gc" for more information.
First, rewinding head to replay your work on top of it...
Fast-forwarded master to dc128e5968ccc632f7875ece639b0d2c94b170a6.
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!