[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at b1210c0 [NFC][XRay] Account: migrate to DenseMap + SmallVector, -16% faster on large (3.8G) input
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   b1210c0..1b802fe  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 1b802fe34d716f2a3542fad3e8ba74f77685590d.
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!