Build native image source jar

[ebaron]

Description
I would like the ability for Quarkus to produce a native image source jar without also running a native-image build. The scenario in mind is the following, with two machines:

1. Maven builder machine with all needed dependencies, but no GraalVM/Mandrel.
2. Container builder machine using a Mandrel builder image, but no Maven or dependencies. It has access to the output from the first machine.

I cannot find a way to perform a Maven build with Quarkus, such that the output jar can be passed to native-image and produce a working executable. When I give native-image the standard runner jar, or uber-jar, the executable exits immediately with exit code 1.

Implementation ideas
This functionality could perhaps be added as a package type selection for the quarkus.package.type property.

[quarkus-bot]

/cc @galderz, @zakkak

[ebaron]

/cc @jerboaa

[geoand]

This would be very easy to add, the question is whether we want to support it or not :)

cc @gsmet @stuartwdouglas

[jerboaa]

@geoand I've had a discussion about a similar workflow with @tqvarnst. The basic idea would be to do everything needed up to - but not including - running native-image. In fact, we've coined an idea of writing the native image command to a file (or just the native-image args) so as to be able to run the native-image command at a later stage. This would be helpful for a staged container build, and debugging native-image builds outside quarkus-maven-plugin. For the former, consider:

1. Compile the Java files and produce necessary artefacts in tooling container A
2. Run native-image on tooling container B using A's output (jar artefacts and native-image args)
3. Take the result from B - the native image of the app - and put it into a runner image C

Each step along the way minimizes the needed dependencies in images A, B and C. A workflow like that could also be used in build pipelines. Please consider implementing this.

[geoand]

Understood.

I'll create a draft PR later on with a new package type as requested and we can discuss further based on that

[jerboaa]

Thanks!