[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 31a3aca [gn build] Port c17da8676a0
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   31a3aca..c9d6fe6  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to c9d6fe6f7d84f5b1a0bdbe502ebc3c8035722fdb.
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!