[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at a868255 [X86] Delete redundant 'static' from namespace scope 'static constexpr'. NFC
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
Current branch master is up to date.
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!