CI: use newest compilers for checks
CI: use newest compilers for checks

We've got a couple CI jobs that run additional checks: AddressSanitizer
and extra compilation flags. Newer compilers might bring improvements to
these checks, so let's run them with the latest compilers.

newsboat/newsboat,newsboat/newsboat,newsboat/newsboat,der-lyse/newsboat,der-lyse/newsboat,der-lyse/newsboat,der-lyse/newsboat,der-lyse/newsboat,der-lyse/newsboat,der-lyse/newsboat,newsboat/newsboat,newsboat/newsboat,newsboat/newsboat,newsboat/newsboat,der-lyse/newsboat,newsboat/newsboat