[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at dce03e3 [InstCombine] Tweak funnel by constant tests for better shl/lshr commutation coverage
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   dce03e3..7b5dfb4  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 7b5dfb400a67f03122b43cd5d59b8b1ef6d00147.
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!