[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 69cd776 [CodeGen] Apply 'nonnull' and 'dereferenceable(N)' to 'this' pointer
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   69cd776..33ca0b0  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 33ca0b0ea619078440b676d136cfda35dfa02e01.
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!