[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at cdead4f [PowerPC][NFC] Fix an assert that cannot trip from 7d076e19e31a
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   cdead4f..4b14ef3  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 4b14ef33e81c01632e848e7a67ccc6b11fb4c595.
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!