update llvm/clang stack
the version in our repo is out-of-date.
a short read with Arch's PKGBUILD gives that we need to import python3-recommonmark
which then requires sphinx to be updated.
which in turns requires us to import sphinxcontrib-* packages so that sphinx won't complain about missing feature when dealing with building python3-reommonmark.
ps. python-commonmark is also a dependency of python-recommonmark.