[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 1ae766e [InstCombine] Add tests for select(freeze(undef)); NFC
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   1ae766e..1f4aa30  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 1f4aa30a4f8a3fb869baa741662b9f6b3c73a0e3.
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!