[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at bfc7636 [LLD][PowerPC] Add a pc-rel based long branch thunk
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   bfc7636..331dcc4  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 331dcc43eac28b8e659f928fd1f1ce7fd091e1e3.
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!