[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 79a69f5 [X86] Error on using h-registers with REX prefix in the assembler instead of leaving it to a fatal error in the encoder.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   79a69f5..9fbb060  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 9fbb060418e00ed7ee3cc88fdd9b90d78b2623a5.
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!