Add linkage type for Pub packages (Flutter / Dart)

[sschuberth]

I concluded it was not supported because for Pub packages (Flutter / Dart) the dependencies were not indicated as statically linked.

Should I report that as a separate issue?

Originally posted by @timovandeput in #3084 (comment)

[timovandeput]

FYI: To my best knowledge, Pub packages can only be statically linked because they end up in a single integrated binary executable.

[sschuberth]

At least https://flutter.dev/docs/development/platform-integration/c-interop#dynamic-vs-static-linking describes both, so I'd assume also both is possible, and we need a way to detect the linkage type. But I'm no Flutter / Dart expert after all...

[timovandeput]

That specific documentation refers to the integration of (e.g. a statically linked Pub package) with native code that interacts with native Android or iOS code. So it relates to the static/dynamic linking of native code within the library that is exposed by Pub.

I don't believe these dynamically linked libraries are in any way exposed via Pub.