Make codegen treat inline fns the same as regular fns in non-opt builds

[michaelwoerister]

See #53963 (comment) and following. There's no need to create private duplicates of #[inline] functions in debug builds, since we don't even run an inlining pass there.

[jonas-schievink]

Wow, is this still an issue today?

[michaelwoerister]

We generate an internal copy per crate (but not per object file). We could probably make use of the -Zshare-generics infrastructure for making inline functions available downstream.

Wow, is this still an issue today?

I think the tone of this comment is inappropriate. Please keep it civil.

[jonas-schievink]

Sorry, I didn't mean to come across like that. I was just surprised to see this issue still open, since I though this was already implemented.