[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 5b354d2 [lldb] Make symbol list output from `image dump symtab` not depend on internal ordering of DenseMap
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   5b354d2..f9091e5  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to f9091e56d34fc1a14fe4640b95a691d9ac7afcc4.
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!