[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 624fc63 [SCEV] Re-enable "Use nw flag and symbolic iteration count to sharpen ranges of AddRecs", attempt 3
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   624fc63..4c0a016  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 4c0a016927872c0c820c0ea5507df102fd8b9b58.
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!