Enhancement Description
Add main opts to {{-Sdescribe}} output. This could simply be a new {{:main-opts}} key along with a string value representing the content of the main opts cache file, if one exists, or an empty string otherwise.
Rationale
Downstream execution environments can make use of the main opt information when using {{clojure}} for dependency download, classpath construction, and main opt selection via aliases. Another way to look at this is that, in the same way that {{-Spath}} provides useful information when composing {{clojure}} with other executable environments that can consume classpaths, access to the main opts is also similarly useful when composing. This need probably isn't sufficiently strong to warrant polluting the options list with a new {{-Smain-opts}} flag; putting this into {{-Sdescribe}} output is likely sufficient.
A secondary rationale might be that this could be useful to humans for debugging purposes.
Implementation Considerations
This could be as simple as a single new line in the script, perhaps placed after the line that emits {{:main-aliases}} in the {{-Sdescribe}} output.
:main-opts "$(cat "$main_file")"
This would work for most normal use cases, but could perhaps be dependent upon what happens with TDEPS-56, where there might end up being some platform-specific changes made to properly handle the case when a main opt has a space embedded in it. (Perhaps in light of this, {{clojure}} could take the stance that {{:main-opts}} isn't guaranteed to be final; this is consistent with things still being in alpha, and perhaps also consistent with {{-Sdescribe}} not really being formal API.)
