[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 27e9f0f [KnownBits] Merge the minimum shift amount and leading/trailing shift value bits handling.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   27e9f0f..30b5c3f  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 30b5c3f3a647ce9c5d3d2db5439592f9f00697c7.
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!