[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at cfc76d2 [gn build] Port fba06e3c85a
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   cfc76d2..e7d9182  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to e7d9182a666a2a8f903bd330c82d7c623b783371.
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!