[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at ad3d6f9 [SelectionDAG][X86][ARM][AArch64] Add ISD opcode for __builtin_parity. Expand it to shifts and xors.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   ad3d6f9..7d3825e  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 7d3825ed954aa1578790b96a8a544d034ea112f6.
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!