> depends: fix osx build with clang 16
>
> For some reason the previous syntax worked with clang 15 and below, but
> clang 16 requires that the option and value are properly separated.
> depends: remove redundant stdlib option
>
> Use of -stdlib++-isystem gets rid of any system c++ header include paths and
> negates the need for this option. In newer versions of clangs the combo
> produces a warning.
> depends: modernize clang flags
>
> Fixes builds with llvm >= 11 in guix by working around the problem. As a bonus,
> this is much cleaner and more maintainable than what we had before.
This is a backport of core#27328, core#27721 and core#27798
The change to ci/test/00_setup_env_mac.sh in core#27798 to ignore -Wunused-command-line-argument warnings seems equivalent to D3792