[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at c1887e3 Revert "Allow running back-deployment testing against libc++abi"
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   c1887e3..c75a0a1  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to c75a0a1e9dc29be4e00d37d0d00288afc1a6153f.
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!