[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 72ddd55 Use `--allow-unused-prefixes=false` by default for FileCheck in MLIR testsuite
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   72ddd55..86cd233  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 86cd2332ce763dde0e922636bc28789d0c2ad806.
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!