[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at 42ed388 [AMDGPU] SILowerControlFlow::removeMBBifRedundant should not try to change MBB layout if it can fallthrough
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   42ed388..6754caa  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 6754caa9bf21a759c4080a797f23e2b7a77a71e1.
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!