Config readability and current dependency on cfg_aliases #9559

I'm still working on getting a sense of all of the dependencies in this package to see where some opportunities arise in reducing the dependency set and I came across the dependency we have on cfg_aliases though the nix project. It is used extensively in that project because of the platform specific nature of their code and the many cfg statements.

We have a similar setup where for example in the stty package we have this all over the place:

    #[cfg(not(any(
        target_os = "freebsd",
        target_os = "dragonfly",
        target_os = "ios",
        target_os = "macos",
        target_os = "netbsd",
        target_os = "openbsd"
    )))]

As the reader of the code for me its not immediately apparent when reading this why this statement is included all over the place and being unfamiliar with dragonfly I was unaware that the detail shared with all of these platforms is that they are BSD.

The way this dependency works is that you define in the build.rs something like:

cfg_aliases! {
    bsd_platform: { any(target_os = "freebsd", target_os = "dragonfly", target_os = "ios", target_os = "macos", target_os = "netbsd", target_os = "openbsd")) },
}

and then in the code itself you use:

#[cfg(not(bsd_platform)))]

The onboarding to do something like this isn't that difficult but wanted to first see if this was something the maintainers were interested in doing?