[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 927afdf [lldb] Skip test_launch_simple on Windows
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   927afdf..dd892a3  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 dd892a33e1ec28ff430c74b67d076344c51e4acb.
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!