[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at c22dc71 [CodeGen][X86] Remove unused trivial check-prefixes from all CodeGen/X86 directory.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   c22dc71..c5cc2d8  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to c5cc2d8b945a23e32613014b5de5d8d7f0c3cfe6.
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!