[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at c6ca26c [IndVars] Remove monotonic checks with unknown exit count
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   c6ca26c..b69919b  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to b69919b537fffcc5b6aaa6d78e2c039725a81f5b.
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!