[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 7dcc889 [SCEV] Generalize no-self-wrap check in isLoopInvariantExitCondDuringFirstIterations
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   7dcc889..e4d2793  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to e4d27932a59fb61aaba3ff7a3ccd1b5bc9215fb9.
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!