[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at ad1fe39 [MLIR] Fix gcc5 in D89161
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   ad1fe39..6771b98  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 6771b98c4e4d5c0bd0a78a876bd212a76ec80a24.
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!