[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 119e455 [SLPVectorizer][X86] Remove unused check-prefixes
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   119e455..00808e3  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 00808e321c724bd9f2a822bce87fe7fe87376371.
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!