[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at a0017c2 [MemorySSA] Be more conservative when traversing MemoryPhis.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   a0017c2..99e865b  master     -> origin/master
Auto packing the repository for optimum performance. You may also
run "git gc" manually. See "git help gc" for more information.
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 99e865b618f31c69776273a60addbd88917a29d9.
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!