How to announce new optional dependencies? [was: What KDE would like distributions to do]

[Matthias Klumpp]

One way to ensure new options get noticed is to enable them by default
and make cmake fail in case they're not supported and - in that case -
have the user explicitly disable them.
With that, the *BSDs will have a couple of -DFROBNICATE=OFF lines in
their package build scripts, but it also is immediately obvious that
way which features they should ideally implement. And for Linux,
distributions will investigate the build failure, find the missing
depndency or other requirement and rather satisfy it instead of
disabling the feature (and again, in that case we would have a visible
flag in the build script).

It does make cmake scripts a bit more complex, but I think that's
absolutely manageable.
Cheers,
    Matthias