[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at ed8982d [libc][NFC] Switch math tests to the new ULP based tolerance.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   ed8982d..364cd76  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 364cd768a2764211ec0cbcf0c0bdbe4d8f4565b9.
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!