[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 60c889c [ThinLTO] [test] cache.ll: Prevent Spotlight indexing of the output dir
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   60c889c..8dbe9b2  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 8dbe9b249846be81bc676543698db14ee37e28e2.
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!