[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 1f4aa30 [MLIR][SPIRVToLLVM] Branch weights support for BranchConditional conversion
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   1f4aa30..334a702  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 334a7025e0d1dd79e3c6b1976be65296ab3da01d.
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!