[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at c72358b [RISCV] Use (not X) in instead of (xor X, -1) in isel patterns to improve readability. NFC
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   c72358b..25ba6b2  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 25ba6b2bcd1e31d16de06eca7d42c331f9d1cf1e.
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!