[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 6ada9e5 [IRSim] Adding IRSimilarityCandidate that contains a region of IRInstructionData.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   6ada9e5..4a55c98  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 4a55c98fa7bee1e5ab1504db20ca4d7c8a083111.
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!