[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 1cab3bf [InstCombine] matchBSwapOrBitReverse - expose bswap/bitreverse matching flags.
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   1cab3bf..e6c4d88  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to e6c4d880fa8c1fdb55850cccd5d56050b7f3ecc5.
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!