--show-compilation-options

$ man mail.mailutils
       --config-help
              show configuration file summary

       --show-config-options
              show compilation options
                   ^^^^^^^^^^^

Well I would then have both:
       --show-compilation-options
       --show-config-options (deprecated)
              show compilation options

Why?

First, we don't want to break scripts, so we'll leave
--show-config-options, but mark it as deprecated.

Second, certainly --show-compilation-options is what this option really
should have been named, so we'll add it. (So please add it.)