[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 5d79664 [take 2] [libc++] Include <__config_site> from <__config>
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   5d79664..ba60de5  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 ba60de5250ce1c4baa4a7bb7098ac67349f88a99.
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!