[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 9922dde [test] Delete redundant lldbutil import, NFC
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   9922dde..e1eeb02  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to e1eeb026e66c38add2a1f8f1271e1f618c2f7a72.
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!