[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at e6e7371 [gn build] Add missing dependency to Extensions
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   e6e7371..4e4f926  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 4e4f926e83cf77f0d36b821a3d2aa1de78338a82.
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!