Provide Way to Handle Multiple Jars with Main-Class Entries

[jamesward]

Sometimes projects have dependencies containing Main-Class entries in their manifests. Since this buildpack picks the first Jar found with such an entry, this can lead to not picking the right Main-Class. Perhaps an env var could be used to specify a glob for the desired Jar containing the right Main-Class.

[dmikusa]

Seems totally reasonable, tagged as an enhancement.

[matejvasek]

This would be really nice to have.