[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at c74da05 [CMake] Make sure _cmake_system_name has a default
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   c74da05..62c3727  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 62c372770d2e87f3e882a20d43c6814e6c4fe0f5.
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!