[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 1013468 [libc++] Temporarily force-set the LIBCXX_TEST_CONFIG cache value
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   1013468..e1d5f7d  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to e1d5f7d003748843f9fd1d1b2d46d3f362b1b5cf.
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!