Wanting a singular packaging tool/vision

IMO, for build dependencies you can get pretty far with a namespace system and a few initial namespaces, e.g.:

  • pkgconfig:libssl for a C library (on Unix)
  • command:cc for a C compiler (on Unix)
  • conda:clang for a Conda package
  • crate:pyo3 for a Rust crate

Perhaps allow ORing them together (command:cc or conda:clang or something-for-windows), and warn (fail later) if all namespaces in a group are not recognized/checkable/installable.

For run-time dependencies, specify names of the actual shared libraries the extension needs, and names of the commands it calls.