[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 20f87d8 [InstCombine] computeKnownBitsMul - use KnownBits::isNonZero() helper.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   20f87d8..a585228  master     -> origin/master
Auto packing the repository for optimum performance. You may also
run "git gc" manually. See "git help gc" for more information.
First, rewinding head to replay your work on top of it...
Fast-forwarded master to a585228027a0f025011d77916234cfba12e44309.
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!