[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at c39c216 Rename AnalysisManager::slice in AnalysisManager::nest (NFC)
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   c39c216..031554e  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 031554ed46c8540e8efdf5dde4c10ddd156ac1fa.
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!