[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at bf36e90 [GlobalISel][CallLowering] NFC: Unify flag-setting from CallBase + AttributeList
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   bf36e90..6b1f9f2  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 6b1f9f2bd4437910804d571284b7c5bb66eac250.
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!