Introduce a -print-targets flag to the odin build and odin run commands to expose the list of all available build targets

[novusnota]

Currently, there's no way to know what are the targets that can be set via the -target: flag unless one pokes at Odin's sources and CI workflows. While that may not be a big deal for advanced users, as a general UX improvement it would be nice to have the list either present in the help doc right under the description of -target:, or be exposed through -print-targets.

There's a similar flag in clang that does almost exactly what I'm suggesting here.

Essentially and as far as I can tell, to implement it for Odin one just needs to expose the strings from the named_targets array that is defined here.

[laytan]

You can actually do -target:"?" currently to get this list, but that is a little bit hidden.

[novusnota]

Awesome, thanks! It'd be great if that bit of info was added to the -target help text :)

[flysand7]

I'm pretty sure -target:? doesn't work if you don't provide an argument to odin build, or there was something weird like this, which I don't know if it got fixed.