[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at e7d9182 Enable constexpr on BITREVERSE builtin intrinsics (PR47249)
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   e7d9182..901e331  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 901e3317fe7c88405b232b090896ae0d111c8c93.
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!