[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 5f6bee7 [Statepoints] Spill GC Ptr regs in FixupStatepoints.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   5f6bee7..9240e48  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 9240e48a588ccdd766a60a307cf6ea028b3106b6.
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!