[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 901e331 GlobalISel: Merge FewerElements for G_BUILD_VECTOR/G_CONCAT_VECTORS
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   901e331..8e06bf6  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 8e06bf6b3a2e8d25e56cd52dca0cf3ff1b37b5d1.
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!