[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 396e7f4 [mlir][SCFToGPU] LaunchOp propagate optional attributes
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   396e7f4..a399d18  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to a399d1880bc6e2a13cad02a2a3cb024c27d32ac2.
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!