[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at e1b5fcb [InstCombine] Add additional trunc(shl(x,c)) -> shl(trunc(x),trunc(c)) vector tests
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   e1b5fcb..97e7fbb  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 97e7fbb343e2a4ea913686254105b9965c5468f8.
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!