[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 68e1a8d [X86] Defer the creation of LCMPXCHG16B_SAVE_RBX until finalize-isel
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   68e1a8d..93db4a8  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 93db4a8ce6261dc36e233f5e0b60cfbb3ea1bd8f.
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!