* install unversioned `llvm` so that it pulls the latest one.
* disable `uninitvar` check on cppcheck as it catches some false positives and
gcc/clang/clang-tidy are good at catching uninitialized variables already.
Reviewed-on: https://codeberg.org/nsxiv/nsxiv/pulls/348
Reviewed-by: explosion-mental <explosion-mental@noreply.codeberg.org>