[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at df3e903 [llvm-readobj/libObject] - Get rid of `FirstSym` argument. NFCI.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   df3e903..699089f  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 699089f2a9702baa987dc2dbe915a2c845c7027f.
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!