[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 777ca48 Revert "[SystemZ][ZOS] Porting the time functions within libc++ to z/OS"
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   777ca48..3ce5f95  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 3ce5f957165d01b5123dfc62429f5ed1d1b6103d.
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!