[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 7b5dfb4 [mlir] Add support for diagnostics in C API.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   7b5dfb4..4a7e762  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 4a7e7620d6c64b9421f939f72e25c28563683eb7.
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!