[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 41ba9d7 [PowerPC] Support constrained vector fp/int conversion
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   41ba9d7..1bc45b2  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 1bc45b2fd8083036c7d5a1545874ab06ec9b029a.
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!