Do not use the full path in generated process types

[dmikusa]

Describe the Enhancement

When the buildpack runs, it generates process types to run the native-image executables. It generates a full path like /workspace/my-super-cool-app. Instead, we should use ./my-super-cool-app. The app will be executed from the application workspace so it's not necessary to prefix the path.

Possible Solution

Modify build.go to generate different commands.

Motivation

This is not presently a problem, but theoretically, the /workspace or application directory can change between the build and export phase. So the platform could provide /workspace at build time and /app during export, so the image is generated with /app. That would obviously break the commands generated because they hardcode in the full path.

We're not seeing any platforms that do this presently, but this would be a minor change to make the buildpacks more flexible.