[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 13e19d2 Revert "[InstCombine] Canonicalize SPF_ABS to abs intrinc"
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   13e19d2..c0e7f64  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to c0e7f64685789520ad732d9dd6bf388dc916e518.
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!