[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 7656dd3 [libc++] NFC: Reindent the feature test macro generation script
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   7656dd3..d6ac649  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to d6ac649ccda289ecc2d2c0cb51892d57e8ec328c.
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!