[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at cc7bf9b [X86] Allow 32-bit mode only CPUs with -mtune on 64-bit targets
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   cc7bf9b..12541b5  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 12541b5ed59d00c6a2ac90ccaf7aa8ff37d8d84b.
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!