[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 4ba0061 [llvm-readobj/elf] - Fix the PREL31 relocation computation used for dumping arm32 unwind info (-u).
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   4ba0061..9b0b096  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 9b0b09671cddf0283f1a8b351dfec10aff6c3dc2.
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!