[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 2e4a20f [SyntaxTree] Split `TreeTestBase` into header and source
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   2e4a20f..399e459  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 399e4593431cf146c52fc286670f88d6217db631.
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!