[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at db1ec04 [ValueTracking] Remove a stray semicolon. NFC.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   db1ec04..3fe01f0  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 3fe01f0e215b7a41481806698efa087be6fe8897.
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!