[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 53f36f0 [Legalize][ARM][X86] Add float legalization for VECREDUCE
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   53f36f0..f6f3402  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to f6f34024e9a4870eea6733dcbab6de89cc435262.
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!