Since `8.5.0` `@swc/core` should be a non-optional dependency

https://github.com/egoist/tsup/commit/fdfd59afb2a9750a4f983cced48b7f4d3b32493d#diff-9290f26e7bf7a9fe9720ea49c795b8f292c16efd2093925f68af2aa9bd411b2fR6 requires `@swc/core` to be installed, to properly get the type.
Either add swc/core as a regular dependency or change that type should be done.

My library uses `tsup` programmatically, and now it doesn't compile anymore.

Start with the linked tsup commit and its referenced diff to inspect the type that now requires @swc/core. Resolve the issue by either making @swc/core a regular dependency or changing that type, then verify that a library using tsup programmatically compiles successfully.

Written by the indexing model from the issue text.