[www-scripts] Clang Attribute Doc Update: ERROR

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UPDATING LLVM SOURCES
HEAD is now at 17eafe0 [X86][SSE] lowerV2I64Shuffle - use undef elements in PSHUFD mask widening
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   17eafe0..b0512ee  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to b0512eed1e9dc03dba4ef8cccee73c13d3487565.
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!