[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at f29645e [gvn] Handle a corner case w/vectors of non-integral pointers
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   f29645e..b8ac19c  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to b8ac19cf1cca5faec8b4404bb0f666cb63c9e1de.
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!