[marcprux]

This PR adds support for the SWIFT_BUILD_SYSTEM environment variable that accepts "swiftbuild" or "native", and the Gradle builds for the various examples will use the specific build system. It also dynamically identifies the output folder for the built libraries so it copies them from the correct place.

This might be used as a template for eventual migration instructions for people who may have been relying on the (soon-to-be-legacy) "native" build system's idioms. CC @swiftlang/android-workgroup as we were discussing this earlier today.

[marcprux]

Note that centralizing the various build scripts into a single shared script (as raised at #39) would make this PR contain less duplicated code, so it might be worthwhile to investigate doing that before merging this.

[finagolfin]

@niktishakov, pull this commit into whatever work you're doing and we'll look at getting both in.

[niktishakov]

Pulled into #56.

[finagolfin]

@marcprux, okay with merging this now? Nik used it in his subsequent pull that's working well, so I'd like to get this in first.

[marcprux]

Yes, as long as at least one person has validated that it works for them, I'm fine with merging this.

[niktishakov]

Thanks, Marc! In case it helps: I checked it in #56, and with your commit all the examples build with Swift 6.4 and the 6.4.x and main nightlies on Ubuntu 26.04, and the APKs have the Swift libraries in them.